After importing my footage in to the Movie Clip Editor, I find that it is not oriented the way I would like.

What is the easiest way to rotate this in Blender?
After importing my footage in to the Movie Clip Editor, I find that it is not oriented the way I would like.

What is the easiest way to rotate this in Blender?
You could add a transformation strip (effect) in the VSE and set the rotation. See the documentation for further details on available settings.

Shift-A --> Effect Strip --> TransformStrip Tab --> Rotation --> 90TRANSFORM --> MIRROR --> X & Y like so:
Transform footage mirroring X & Y turns it "right side" up: