Whatever you do..do not pull the pin out of the new one!!!

You should have a hole that you can fit the new one in. Once the base is through the hole you need to grab the base from underneath ( I used a needle nose plier), pull it down and turn it about 90 degrees, let go and voila! Once you let go it snaps back up at a right angle to the way it went in through the top.

I wrote this quickly but I hope you got it
Hope it helps.