Somebody posted this in another topic and I copied it.
Follow these steps:
1. Send the student a friends request
2. Both go to livechess
3. At the same place where you can choose the time control you want to play at you can also choose "analysis board".
4. If you choose analysis board and then click on start it will open an analysis board.
5. In the right bottom corner you can see your friendslist. Rightclick on the name of your student and then click on "invite to analysis board".
6. Your student has to accept the invitation. Use skype to speak to him while going through moves on the analysis board.
dont know the commands new in chess.com