If you have been given permission to rotate pictures in an archive, you can select one or several pictures and open the Asset Information panel where you find the Rotate buttons near the bottom of the Information tab.

These button allow you to rotate the selected picture(s) in steps of 90 degrees.

Simply click on one of the rotate buttons to execute rotation. You don't have to worry about quality loss in JPEG's since the rotation is based on EXIF data only. This makes it possible to rotate even very large files quickly without requiring lots of processing power.