Maybe you should ask the grandkids!
I went through that within the last two weeks and got about as much help as you are getting. Got some sympathy from a self-styled "luddite", but no clues.
I finally realized that if you make a reduced size copy and save it in your pictures you can then follow the "additional options" button when you are drafting your post. I used 25% of the normal size. (in PICASA, Right click on image; Edit; Image; Resize; change size from 100% to 25%; save as "small" - if you don't "save as"- with some additional description you will end up with only one copy, but "resized")
When you draft your post/reply;
-select the reduced photo you wish to post.
-"Open" will then attach it to your post.
This worked for me, but there may be better ways!