To move the drawer slide to a different rung on the front and back rails, remove the rivet screw that secures it to the front rail, lift the glide upwards out of the front rail, and push the glide ...

Simply get some gloves or an old rag, put a bit of the wax on it, then slather it on the middle and side rails. If your wood drawer is getting stuck in certain areas you can also wax those places ...