You will need to have made a few more posts before you can add attachments to a post by clicking on the paperclip icon (it's an anti-spammer measure), but you may be able to use the insert image option...that's the little icon that looks like the landscape icon on a camera. Click on that, and you can navigate to the photos on your PC, select them and insert them. If it turns out that you need a few more posts to do that too, leaving a few comments in the gallery counts towards your post count.
The Buy/Sell/Trade forum is found here:
Buy / Sell / Trade - Splitcoaststampers
There's a section with FAQs and guidelines, and then you would want to start a thread in the Buy & Sell section. Thanks for asking about how to share the photos, Susan, because uploading them to the gallery would not be appropriate and they would just be removed.