Sarah, if the photo is not already in an album. Go to Gallery, select catergory, I selected Family. Then I uploaded a photo of Tori and her brothers taken on her 12th birthday. That is just sitting in the Gallery not in an album. I then selected the photo again from my list of photos. It seems as if it has to be uploaded into one of the catergories in order for it to load onto the blog.
I am no expert on this but that is what I just did to achieve this result.
To add a whole Album to the blog as I did for my last blog on my grandchildren go "Add Blog" from there to "Entry Album" slot, click on the Album you want from your own list and it will be added to the blog.
If this does not work for you please contact me again and I will see if I can find a workaround.
This applies to anyone else who tries to do the same thing.
( My sons would laugh at their mother thinking she knew what she was doing...lol.)