Hey friend,
It would seem to me that you are new to this game. Considering that, I will use some simple terminology which isnt meant to be insulting and is mostly because I dont know the proper names for the things I am describing.
You know the window that you can toggle sit/stand, you can camp (exit game), toggle run/walk, etc? That window should have 4 tabs.
1.the one i described above
2.abilities
3.combat abilities
4."hotbuttons" (page of useful premade hotbuttons and 9 pages of blank ones for you to make your own)
Having not played a pally, i cannot tell you if it will be under abilities, combat abilities, or both.
All you need to do is click one of the empty "buttons" and set it to be lay hands when a list pops up. Then, you can do a long click on your lay hands button and transfer it to your hotbutton bar.