Retru, I think Psyduck314's referring to the in-game hotkeys and action palette.
Hit F12, go to Customize, there you can assign items, techs and traps to your action palette. (hit CTRL to swap modifying between the two palettes)
While in that function, you can go to all the available items, techs and traps and assign up to 10 to your hotkeys (1 thru 0, number keys on top row) by selecting the item/tech/trap and hitting that number key.
Once all your assignments are made, just exit the Customize function via the ESC key.
Hope this helps, good luck!