Well, first things first, you have to upload them to a site.
You can go to
here , make an account, and upload pics.
After you upload your pics, it will give you three options. Normal link, tag link, and an image link. You'll want to take the image link, and then copy and paste it into the forum.
When you copy and paste it, it should look something like this before you submit your post
Once you have that in, it sould have a pic there instead,like this:
I would preview my post beforehand, just to make sure the pic shows up.
Hope I have helped!