The best solution is to create an account on github and store your model project in revision control. Then you can make changes locally on one machine, push the changes up to github and then on the second machine pull down the changes. Make changes on machine 2, push, repeat. Here is an example of an xtUML model in github: https://github.com/xtuml/models/tree/master/applications/futbol
Of course, this requires that you learn a bit about using git. Module 5 in the xtUML Modeling online course will get you started.
If you truly want to go the export + USB stick route, there are two options. See units 4 & 5 of Module 6 in the online course.