I can hear the excitement in your post and that's lovely. As far as posting pictures and in which threads, generally one will post in the Introduction section first. (That is the first section at the top of the Board Index). In each section, at the top, there is an information thread about how to post pictures using Photobucket. That is the easiest way.
Once the pictures are uploaded on your computer, you simply go to Photobucket, create an account and upload there. Follow the instructions and away you go. The other members will also help as you go.
As you can probably see from the various titles of the different sections, we cover every topic, and then some. In the "General" section, there are all sorts of topics from Misc. Idle Chit Chat to What did your dog do today to make you laugh and even ones of individual dogs. I just made a thread in there called "Oliver & Henry's Antics" with pictures.
We even have an "Off Topic" section that has all sorts of interesting and silly threads, like recipe sharing or pictures of our gardens. Just have a look around, and please feel free to jump in to any thread that interests you. There is a Breed Specific area, as well as a Behaviour Section, just to name a few.
If you ever need specific advice, please feel free to send me a Personal Message. Have fun exploring the Forum, and the whole site and don't worry about being in the right or wrong place to post. We Mods can always move a topic and are happy to offer guidance.
You may wish to wet your feet in the Introduction section. You don't need a dog to post in there, as we all enjoy talking about the impending arrival of a new one. Actually, several of our members are without dogs. The only requirement here is to love dogs and you certainly fit that bill.
I am excited that you have contacted a rescue group and are moving forward. Keep us posted, and start exploring the DP!