Open LW on your downstairs computer, tools > options > saving. That will show you the location of your saved folder, with all of your saved files in it. You can find that folder on your computer, copy it to an external drive or disc & then copy it onto your upstairs computer.

Or, you can go to the downstairs computer's LW library & click on Saved Files. Now highlight a file & click Explore (bottom left)... that will open your saved folder. From there you can select files to copy, if you don't want to move the whole folder

Once you have the files copied onto a disc or drive, you can add them to your LW saved folder on the upstairs computer (in LW tools > options > saving to show you the location of the folder that you need to add files to).

If you want to share those new files on LW, go tools > options > sharing. And now you'll be able to browse your computer & add the folder with the downstairs computer's files