It usually looks like a paper-clip. Click the attach button. Wait for the prompt to show you that it has been added, or for its' name to appear on the attachment list in the e-mail window. You have now added the photo to your e-mail. Repeat this process for each photo that you would like to send.
Some mail programs limit the size and number of attachments.
If that is the case, you might have to send more than one email. It does no good to zip a JPEG image. If there are differences, send as many photos as you would care to. Also photograph anything unique to the package, such as an inside gatefold, insert, booklet, close-up of sticker, etc. How to photograph Photograph each item separately.