Get a key, use it normally on the door its for, and it will 'attune' the key. Then you can type /key to see what keys you have and it will be listed. from then on, you dont need the key on hand to use the relelvent door / portal.
For example, make your trakanon idol for access into old sebilis, then walk over to the big black ball and click it with the idol on hand as normal. then your /key should show 'trakanon idol' and you can click on the ball with nothing on hand and get in. My idol is still in the bank, but you can probably destroy it, I'm just paranoid. :)
-Syresia of Nameless