This page has guidance on many platforms which your children may use - all the information is there to help you keep your child safe.

Please check your children's devices regularly: look at all chat messages, internet history, check privacy settings; check who they are following on apps e.g. TikTok are appropriate and so on.  

There is also lots of advice you can find on the NSPCC website:  https://www.nspcc.org.uk/keeping-children-safe/online-safety/access-to-technology-for-different-ages/