Hi Bundybear + welcome to pixalo
First you upload photo's to your gallery : Click on the Members Gallery link at the top right of any page + you'll see a link "Upload Photos". Fill in the details to upload your photo. It will appear in your personal gallery as well as the "Recent Photos" on the main Gallery page, as well as in the category that you choose from the drop down list.
Then you start a new thread in the Sharing or Critique forum. To get your image in the thread, copy the UBB Code you'll find underneath your image in your gallery + paste the code in.
There you go
Any prob's just shout.