Hey Simanova
1) Facebook - posts and video embedding. So just click on the facebook icon above (BBC tags) when you post and put the link inside.
2) Twitter - paste twitter post links without tags. It should show up automatically.
3) Social media share posts - above or below each topic there's a share button.
4) Profile social media share - go to "profile" "forum profile" on the left hand side, then scroll down to add your personal social media contacts and it should show up below your avatar. For example, I've added twitter to my profile.
5) Periscope .... working on it.