Courtesy of @Gt city
How to use weekend code:
In the game:
1. Press Social Button (3 people on it)
2. In menu opened, press similar icon again.
3. In the opened windows, click last tab "Add Friend"
4. In field below, where it is written "Please enter friend's username to..." enter full code (include the asterisks) and then click "Add" button. Voila!
However the codes usually only work from Friday until sometime Monday morning so you will probably have to wait for next week's code
How to use weekend code:
In the game:
1. Press Social Button (3 people on it)
2. In menu opened, press similar icon again.
3. In the opened windows, click last tab "Add Friend"
4. In field below, where it is written "Please enter friend's username to..." enter full code (include the asterisks) and then click "Add" button. Voila!
However the codes usually only work from Friday until sometime Monday morning so you will probably have to wait for next week's code