Several or a lot of them?
If several click Go Advanced in either a New Post or New Reply window, type your post, then in the 2nd window down click Manage Attachments. Follow the prompts and the photos can be inserted from your computer (Currently Full Size only) to your posts.
If you have a lot of them you may want to upload them to the
Scubaboard Photo Gallery first.There anyone can view them, comment on them, and you can copy them to posts as desired. The first time you use it you will have to login - use the same user/pw as you do on the forum - from then you should be able to go between the forum and the gallery w/o having to re-login.
A third option is that if you already have them stored on an external photo sharing site like Photobucket, Picasa, Filckr etc. they can be viewed/referenced in your post here. Most of the photo-sharing sites will provide the necessary code. You want the BBCode not HTML.
Lastly if you know the URL of the specific image - click this icon -
found in the toolbar in most post/edit/reply windows and insert it directly into your post. If you don't see the toolbar in the window you're in - hit Go Advanced.