If you are on a "windows" PC.
Right click on your image or photo and use "Open with"
You should see various options to open; Select "Windows Photo Gallery"
You should see your image...
At the bottom center you will see Rotation arrows, choose and click "Rotate clockwise"
The image will turn thro 90 degrees
To save the image - click the little arrow next to "File" [at the top bar] and choose "make a copy"
the changed rotated image [With a different filename as required and yhen upload]....
Hope you followed that....
Oxie...