Why don’t you use the software directly to stitch? It will give you the panorama mode (the one where you can move).
If you’re interested in using an already stitched image then you can use look at what was said here Importing an already stitched video
But I don’t recommend that. The software should be able to handle everything, from the two separate raw videos to the final result.
Let me know if it succeeds. If it does not, or if you have any issues, let me know, as I am rewriting things and will soon drop a very big update.