An easier way? (at least as of version 8.35 but as I write this I believe 8.97 is the current version and this still works)
When you add your video file to your project, it appears in the "video file bin" in the top left.
Right click on the file and towards the bottom of the menu there should be an option called "Rotate Clip".
In that menu the choices are to rotate by:
0° (degrees)
90° (degrees)
180° (degrees)
270° (degrees)
Then after rotating the clip in the video bin, you can drag it into or insert it into your project.
Done!