Hi maryclewis - welcome!

To upload a photo directly from your computer, just make sure it's under 250k or compression will occur. (click manage attachments when replying and u can do this)

To attach a photo from a 3rd party like flickr, just right click the photo you want and choose copy image location (or something like that for your particular OS).

Then click this icon above and insert the URL.

Hope that helps - Marko