There are several alternative ways:
- While playing the game (on pc) press keys Print or Alt+Print to take a screenshot. Then change to a graphic editor software / picture viewer (Microsoft Paint, Paint.net, IrfanView, …) and paste the screenshot from the temporary storage to the programme (simply press STRG+V to paste). Whether you can edit the screenshot or not depends on the software you are using.
- If using Firefox Quantum, use Firefox Screenshots.
- Or use a browser add-on, such as FireShot for Firefox or Chrome.