If you receieve a new pm, then you can access it via a number of options:
1 - look at the top right corner of the screen and you will see the "1 new private message" icon - simply click on that and you will be taken to your inbox.
2 - Go to your profile page and click on the "new message" wording which is in the middle right of the page, you will then be taken to your inbox. Even if you have no new message, there will still be something that says "you have no new messages" - you can still click on this to access your inbox.
3 - Via the Community home page -
www.wikivorce.com/divorce/Community-Home-Page/ - look own the left hand side of the page, and you will see a list of options - including "my inbox" - click on that and you will be taken to your inbox.
4 - bookmark your inbox page so you can find it quickly and easily.
Once you have accessed your inbox, you will be able to read all your pms (past and current) and also send messages from there, and read previously sent messages - pretty much the same concept as most email accounts.