Hi Julie, and welcome. I'm glad you found your way here. :)
To answer your questions, the best places to find 'starter' information about the site is on the Help page and on the Q & A page. Other than that, feel free to just make a new post in your own blog with a question and someone will answer (if you get the 'access denied' message, it might mean you're not logged in).
Also, all new posts show up on the 'All posts' page, so go have a look there if you want to see what everyone else is posting.
Last thing, if there's a subject you want to know about, just type the key words like 'mastectomy' into the search bar (you'll see it just above the main navigation, where it says 'start your search here'). The results page will show you all the website pages and posts that match your request (see the label on the right side of the page).
Hope that helps, feel free to send a personal message any time if you get stuck. :)
Di