Wherever possible, having computers/gaming consoles in communal areas of the house, leaving phones and tablets downstairs at bedtime, monitoring the time spent and who children are communicating with is ideal. CEOP (Child Exploitation and Online Protection) is a law enforcement agency which is tasked with protecting young people online and where issues can be reported (https://www.ceop.police.uk/safety-centre/) and Thinkuknow (https://www.thinkuknow.co.uk/) is the educational platform from the same organisation, designed to help teach online safety for children of all ages.
If you have concerns while playing a game you can click this button to report it. You must speak to an adult or alternatively you can call Childline 0800 1111
Setting restriction on android devices:
Useful website with suggested age ratings for different apps, movies and websites:
Setting restrictions with your internet service provider:
Creating More Secure Passwords: