You may be asked to turn in a screenshot of activity you perform within a virtual machine. You can do that using the VM's own screenshot software. But then you may need to transfer the resulting screenshot file out of the VM in order to turn it in. That's feasible but it might be easier to instead use a screenshot program that you may have on your host machine. Take the screenshot with the VM window open showing the activity of interest.

If you do want to use the VM's facility, in my provided fedora linux machines yield a screenshot file if you press the PrintScreen key. The result is a file deposited on the disk under a name like "Screenshot from 2020-09-14 21-29-57.png" in the "Pictures" subdirectory of the user's home directory. If you are logged in as student for example, it will be in /home/student/Pictures/.

The host option is recommended in order to avoid the need to transfer the file out of the guest VM, since the VMs as provided are not equipped with interfaces that give them internet/external connectivity. It can be done and is documented on our class website but is best avoided.