Easiest thing to do, put it in from the bottom.Look at the pin one side is always larger, use small end, oil the hole, use a starter punch to get it started leave the starter puch on, insert your forward assist push it in to about where it should be and hold it there while holding your starter punch then give it a few taps with brass hammer until you feel the forward assist being held by the pin, then drive it in about half way...