How does the search function work?

It works great! You have four main boxes: What (a keyword), when, where (which board), who.
Use as few or as many of those parameters are you want.

I would put reading in the what box and leave the rest blank. It will pull up ever post here that has the word reading in the title or the body.
If that is too many then start restricting by putting a specific board in the "where" box or putting in dates around a certain time frame. It is a great search function!

i must bemissing something b/c when i'm on the main nsbr page there is a little box upper right that i typed "reading" into and hit the magnifying glass button, another window popped up wiht some buttons i could filter with and i did that and clicked done and none of the threads that show up have anything to do with reading nor do i see the what where when things

The one on the right is a 'live' search. It effectively filters the board by the word you enter: if you put "reading" into it, every thread you're left with will contain that word somewhere. What it doesn't do is take you to the specific post(s). For that, use the top search as Volt says.

The live search works the same way in threads - it will filter out so you're left just with the posts within the thread that contain the search word. Try it out on this thread using live as your search term and you'll see what I mean.