Are you able to point the launcher to the existing folder using the launcher settings?
Click the gear icon next to PLAY (or INSTALL in your current case). Then it will open up a menu, choose GAME SETTINGS.
From there, choose the World of Warcraft option to see if you are given an option to USE A DIFFERENT FOLDER.
If that doesn’t help, then click this part on the left of the GAME SETTINGS menu.
DOWNLOADS – then click SCAN FOR GAMES
