It is easy to make it harder than it really is. First, create a page called pop.htm Now, take a second to look at the script. I've never setup a script before this one. DO NOT do anything yet. JUST look at the script.
Scripts can be very intimidating just to look at.
So look at it, but that's all. Don't change anything. Copy and paste it exactly as it is. Do that now and then come back here for the rest of the instructions. There are a few things you can change if you like.