go to the competitions tab in the editor and search for english premier divsion. Select it and then go to the teams option (in the premier division options), click add and find rangers. You then need to move a team out of the english premier division to keep the correct numbers in the league (if you don't want to remove them completely, repeat the process through the divisions until you're happy). Add a team to the clydesdale premier league to keep their league numbers correct too.