Once you click on the rooms tab, all the rooms will be displayed. However in case if you are trying to enter a particular room and it's not allowing you to enter or asking any kind of code then the room is coded.
To join such coded rooms you need to enter the correct code for the same.
Step:1 In case if it's a coded room, on clicking Enter a PopUp will open up which will ask you to enter the code.
Step 2: You will only be able to enter the room by entering the correct code and further clicking on the join button.