Always make sure you share your whole screen, including URL bar, clock, etc. Make sure you close anything you don't wish to show us.
On a Mac: Command-Shift-3
On Windows: press the Print Screen Key, usually labeled “PrtSc” or "Print Screen". This will save your screenshot on your clipboard.
To save it, the most recommended way to do this is by using the Paste command on the Windows program Paint.
- Start Paint
- Paste by going to Edit at the top bar menu and choosing Paste or using the command CTRL+V
This will save your screenshot as a .jpg file, which is the most common image format available.