Or am I missing how to do it?

I've gone to the enchanting table and tried to equip the item then use the soul gem......I can't figure it out.

The game tells you when your item is drained how to do it. On the xbox you open your inventory and press RB when you are on the item.

Bring up the Menu

Go to Items > Weapons > Pick selected weapon.

It'll say at the bottom of your screen (RB Charge), least that's on 360 at least..

NOTE: SOME WEAPONS HAVE INF. CHARGE! Like Mehrunes' Razor, Valdr's Lucky Dagger, and Ghostblade. These weapons you will NEVER be able to charge with a gem.

On the Xbox, goto the weapon inventory menu, select the weapon and hit the right bumper. This will open a menu with all available soul gems and show you how much they'll fill up the weapon.

Not sure on the exact method for PC or PS3.

Menu > items > Weapons > select weapon > (on. Box) RB > select soul gem > enjoy

Open your inventory and highlight the weapon you want to recharge. A new option is shown at the bottom, the button to press to recharge the weapon. Default for PC version is T, I don't know what it would be for a console version. Pressing the button opens a sub window where you pick which soul gem to use to recharge.

Thanks guy...got scared for a second there.