If you know about pan crop you know how to get to the window - by clicking on the square box near the end of the video. That brings up the event/pan pop up. To the left side of the pop up screen you should see a slider bar with sections highlighted saying 'position', 'rotation', 'keyframe inter'. Below the pop up window with the F and a circle around it is a keyframe timeline. Make sure your slider is all the way to the left (the beginning of your video). There is no need to add a point - just want to make sure you areat the beginning. Click on the number to the right of word angle - this is under the section called rotation. The number turns into a highlighted box. Type in 90 degrees (or whatever angle you need to get it the way you want). Hit enter. You are done. Hit the teeny tiny x at the upper left corner to close out the pop up.

The reason I had you check the keyframe timeline was so that your rotation was applied right at the beginning. If it is applied somewhere else - the software will rotate the thing as time passes - based upon the points you add, which could be fun, but might make you a little dizzy. If you want to have the old batman effect (gee am I showing my age with that reference?) you can type in a huge number so that the thing rotates a bunch of times.

have fun with it!

P.S. You can do this with track motion as well, just keep in mind everything on that track will have the effect applied to it - so if you have other clips you don't want to use it. To use track motion click the box with a tiny arrow in it that is right after the word video on the very left of your view ( it has the word level and an exclamation point etc.) Then do the same thing described above.