Hello and WELCOME!!! I only have 19 orchids.. so your doing good! Let me see if I can help you out with that a little.
When you log in it automatically brings up all the threads with the newest unread posts.
If you want to go the screen that has the different sections and groups of threads click on the enter orchid board forum at the top of the welcome screen or if on another page at the top of your screen click on orchid forum orchid care to get there.
To upload pictures you can either choose the manage attachment option at the bottom of your post when you make a new one and attach them there or you can upload them directly to the site. To upload them to the site go here (I bookmarked this address)
http://www.orchidgeeks.com/gallery/upload.php?c=2 once you upload your photo copy and paste the text in the field next to BB image code into your post and the picture will be there.
You will be automatically subscribed to the posts you reply to and can go into your user cp (upper right hand corner) to view your subscribed threads, you can also choose to view all of your subscribed threads if one want is not listed.
I hope that helps and I didn't confuse you. It took me a while to learn how to get around here because i had never been in a forum before!