OK, well let's try it an easy way.
Store your photos on your computer where you can find them. Sign up for
Imgur.
In Imgur, go to your account name (top RH corner) and click "Images". Then "Add Images". Tick the Auto Resize box to make your photos small enough to go on the forum (1024 is the biggest you can use here). Browse to your stored photos and either drag and drop them onto the Imgur screen, or select them and submit.
Right, now the images are successfully stored on Imgur. Your next task is to get them onto the forum.
Click on the image you want to load. It pops up in a box, with a whole lot of options down the right hand side. Go to the second-from-bottom option (BBCode) and click on Copy.
Go to the forum post you are writing, and right click paste.
Post your post and the image will show.
If it were complex, I wouldn't be doing it. I hate computers. The fact that I post literally thousands of photos means that it must be straightforward. Give it a go.