most of the other websites I use give instant email notification when there has been a reply to a topic I posted

how do I get this to work

Very good question and the fact that I had to ctrl-f this myself to find it means we did a real good job of hiding that feature.

I don't automatically transmit emails to notify for every post/reply because most people here would not like that too much. There is a self-subscribe feature but you have to hunt for it -- look down at the bottom of the screen within the page footer and you will see it. I will add this to the list of things to improve.