Let me tell you, there is no easy way to do this. I was hoping it will come as an update from Blogger but I got tired of waiting. It should be a basic feature when uploading photos, but oh well.
Anyway, here you go:
After uploading a photo and finding that it’s rotated at the wrong angle…
1. Open Picasa web albums
You should know that all your photo uploads at blogger are deposited here.
2. Open your blog directory
It should contain all the photos you’ve uploaded. By default, your folder is named after your blog. If you can’t find it, maybe you can “View All”. It should be there hehe
3. Find the photo you want to rotate
Since it’s a recent photo, it could be all the way down. To make it easier, sort the album by date. How? Click on “Organize”, then on the “Sort photos by…” dropdown list, select “date (newest first)”. Then click Done.
4. Open the photo and “Edit in Google+”
When you open the photo at Picasa you may find that the rotate left/right icons are disabled. God knows why! What you have to do is click on “Action” and select “Edit in Google+”. It will load a new window where, THANK GOD, the rotate buttons are finally enabled!
5. Rotate and go back to blogger 😀
It will be saved automatically. Now you can go back to your blog post, select “Insert Image” and look for the photo you’ve just rotated under the “From this blog” tab. It’s probably all the way down, bummer, I don’t think there’s a sort by feature for this! XD
That should be all! Hope this helps! 😀