If you are accessing the mobile version of chat you can't.
If you are on a desktop then look to the right of the screen and under where your own cam shows it says. "Allow private msgs & pokes from." Then use the drop down box to select which you prefer.
The drop down menu is below where your own cam would show.
When you look at the room list.
General chat is at the top of the room list. The drop down box is just about where it says General chat.
