That's not the way you slot enhancements. You only click on the powers themselves when you want to combine two enhancements. Just open Manage, and drag and drop the enhancement in an empty slot (or over a red enhancement) of the power you want to drop it in.
But to be sure- are the enhancements you're buying the same level as you? If they're red-numbered when you get them, you won't be able to use them in any way.
Okay, I'm not really understanding what you're talking about here. I'm going to try to answer a few things, and hope that one of them is the answer to the problem that you're seeing:
1) Make sure that the attack you're looking at takes the enhancements that you're trying to put in them. For instance, the Katana attacks can't take something like a Hold enhancement, since they don't apply a hold of any sort. They will take Accuracy, Damage, Endurance Reduction, Recharge Reduction, and Defense Debuff, though.
2) Make sure the enhancements are of the right level range. You can only slot enhancements up to 3 levels above you. If you're a level 2 character, for instance, you can slot level 5 enhancements, but not level 6 enhancements. The level of the enhancement is displayed at the bottom of the enhancement. Similarly, unless you're looking at craft enhancements (inventions), you can't slot any enhancement more than three levels under you. So, a level 6 character could slot a level 3 enhancement, but not a level 2 enhancement.
3) Make sure you have open enhancement slots in the power you're looking at. Each power has a certain number of enhancement slots. When you first get the power, it only has one slot. You can add more slots to a power as you level. If you don't have any open slots for the enhancement, the power won't take the enhancement.
Hopefully one of these things helps.
Let me never fall into the vulgar mistake of dreaming that I am persecuted whenever I am contradicted.
~Ralph Waldo Emerson
"I was just the one with the most unsolicited sombrero." - Traegus
thanks for the replies! I think this is a level thing, but I am at work now so I will have to look at it tonight
Feel free to come on back if those steps don't work. We don't mind helping people out here, and if this is genuinely a problem, we can get you in touch with the right people.
Hopefully, however, it's something simple that was just overlooked, and it's an easy fix.
As an aside: you're not a noob. You're a newbie. You're new to the game, but you came here with a question so that you could learn. That automatically makes you not a noob.
Now, if you have come here saying something like: "The enhancement system here sucks, I can only place one enhancement! That's stupid!" That would have been a noob comment.
So, you're many, many steps above a noob. Don't go insulting yourself like that. 
Let me never fall into the vulgar mistake of dreaming that I am persecuted whenever I am contradicted.
~Ralph Waldo Emerson
"I was just the one with the most unsolicited sombrero." - Traegus
From reading your response a few times, I *think* you're trying to "combine" enhancements. You're going above and beyond.
To put an enhancement in an empty slot, just open the manage window and drag it from your tray to the empty slot.
To combine enhancements, open the manage window and drag an enhancement to a slot that has an enhancement of the same type in it. Or, from the manage window, click the power and it will let you combine something from your tray with something in the power.
... which sounds exactly like what you're describing.
If you feel "overly new" consider that I once spent several minutes trying to go in the "exit only" door of the Paragon City Tram.
Mini-guides: Force Field Defenders, Blasters, Market Self-Defense, Frankenslotting.
So you think you're a hero, huh.
@Boltcutter in game.
[ QUOTE ]
If you feel "overly new" consider that I once spent several minutes trying to go in the "exit only" door of the Paragon City Tram.
[/ QUOTE ]
Hell, I did that the other day!
As I was going into the tram, a citizen pushed me out of my path into the out door of the Tram without me noticing. I spent a couple minutes, and almost sent in a petition, before I realized what I was doing.
Also, as a newbie, I thought that enhancements were locked and couldn't be overwritten, so I was too scared to slot any enhancements because I thought that they'd red out, and I wouldn't be able to get rid of them.
Let me never fall into the vulgar mistake of dreaming that I am persecuted whenever I am contradicted.
~Ralph Waldo Emerson
"I was just the one with the most unsolicited sombrero." - Traegus
OK I started a villain (nat stalker katana/regen) in the 14 day trial, I could only get the first attack enhancement to work, nothing else would work. OK, I guess I have to sign up to get them to "go white" in the manage window. Nope. I typically click on enhancement/manage, open a power and none of the enhancements (even the ones that say they should) are usable. I started a new hero (after I bought the game) and same deal. Any ideas?