Not sure what happened in the previous post - 2nd try:
What I did:
1) I created a separate directory for my post pictures in the wp-content directory called postedimages. 2) uploaded all my thumbnails using ftp into the postedimages directory. 3) In admin panel selected write post and used the img tag to add image (need to add the path of the image) and then manually typed in the additional html in my post as I wrote the text.
Here is a recent photo that I wanted to share:
/postedimages/samplephoto.jpg" onclick="window.open(this.href, 'popupwindow', 'width=500,height=708,scrollbars,resizable'); return false;"><img src="http://www.yoursite.com/wp-content
/postedimages/samplephotobig.jpg" alt="My Photo" />
Just copy and paste the above code and then fill in your own info: i.e. your site address, thumbnail directory, image file name, and the size that you want your popup window to be.
Hope this is the answer that you were looking for.