You just have to simply install it from Module Manager.
If you are new in Vtiger, Follow the steps to go to Module Manager.
Click on Gear Icon (Top Right Corner) > CRM Setting > Studio (Left Navigation) > Module Manager > Click Install From Zip Button > Select your language pack zip file and Install.
Note : Make sure you have valid format of zip file otherwise it will not work.
You just have to simply install it from Module Manager. If you are new in Vtiger, Follow the steps to go to Module Manager.
Click on Gear Icon (Top Right Corner) > CRM Setting > Studio (Left Navigation) > Module Manager > Click Install From Zip Button > Select your language pack zip file and Install.