This video is a general introduction to google classroom
If you have to complete a piece of work by hand, you can easily take a photo and upload that as evidence. Or if you do not have access to a laptop/computer, you can download the google classroom app onto a smartphone and view the assignment there. You can then easily upload pictures of your work as evidence.
This video will help you with the functionality of completing assignments within google classroom
This video is by a canadian teacher and is good for detail but uses american terms i.e turn in instead of hand in