Yes - I'll try to find a link here that explains it well, but in the meantime, if you have a photo on your computer (I tend to put the photo icon on the desktop, but I don't think you have to)
1) find a photo site that puts computer photos into jpeg (or gif) format such as photobucket or imageshack, or many others. I like photobucket because using it seems pretty easy to me.
2) sign up to one of those sites and add your photo to it following the site directions
3) click on the image url on the site (on photobucket, I use the 4th one) - that will copy the url (the url being the string of symbols and letters that ends in jpeg).
4) open the reply window on your thread here
5) notice up above the window are "buttons", one of which is IMG. Click that.
6) [IMG] and [/IMG] will show up in the reply window
7) put your cursor inbetween them if it isn't there already
8) click paste on your browser's edit list
9) push preview button to see if the transfer worked
10) if so, push Submit