For the security of all players and their accounts, you may not post URL’s or otherwise direct players to any other websites. Not all sites are designed with the players’ safety in mind, and Jagex can only vouch for the security of their own sites.
The only videos that you may direct others to are those on Jagex's official channels.
You are welcome to mention your social media name/channel, but you should not be creating a thread just to advertise them.
As well, giving links to your social media is not permitted on the forums. From the Code of Conduct:
"You may post your social media name, as long as you do not link to the specific website: ie Follow me on Twitter @example; NOT follow me on www.twitter.com @example. This is to prevent users from linking you to malicious websites."