To attach pics they first need to be on a host site. You can create an album here or probably the most popular is Photobucket.
If you use Photobucket, just copy the photos "Img" code and paste directly into your post.
If you create an album here, open the pic, right click and a window opens. Click on "properties" then copy location. Come back to your post and click on the little yellow box that looks like it has a mountain in it. Paste the copied location in the box that opens.