ALERT: If you have an older translation version already installed you need to remove previous pack and upload a new one.
After finishing you need to perform an "Admin/Quick rebuild" your SuiteCMR instance!
Note: permission issues may prevent your new language to be installed.
1- Login as English
2- Go to Admin / Module Loader
3- Uninstall previous language pack
a) Select pack to remove and click "Uninstall"
b) hit "Commit" to uninstall
c) Back into Module Loader, let's make some clean up: delete old pack
4- Go to Admin / Repair / Quick Repair and Rebuild
5- Logout / Done!
See tutorial here