Lisa, wherever you see the word 'last post' on the right hand side of the screen (it isn't everywhere), just click on the arrow so that it is pointing down and the latest postings will be at the top. They will be under anything that moderators have made a sticky ie important things that will always stay at the top of the page. If the arrow is pointing up, the latest postings will be at the bottom of the page.
I've just had a fiddle with it and found this out for myself although mine was in the right position to start with anyway. I thought there was something else we could change (without going into our profiles) to make sure this happened but have not been able to find it. Any more suggestions from members would be appreciated.