In the web:
In each clan profile, tournament, player, etc. just below its name appears ID / code. Click on it and paste it here.
In the game:
The tag is in your profile in the Clash Royale app.
Once you are in the game, you click on your name to see your profile, once your player card has been opened "profile go", just below your name an ID similar to this appears #D2CVA9, if you do Clicking on this label will give you the option to copy it to the clipboard.
Once this is done, paste the tag here.
