use the launcher to add versions, to update, etc
*** under the Unreal Engine tab of the launcher (top), go into your Library (tab on the left) there you will see Add Versions at the top (try that) *** 
don’t need to install again
use the launcher to add versions, to update, etc
*** under the Unreal Engine tab of the launcher (top), go into your Library (tab on the left) there you will see Add Versions at the top (try that) ***
don’t need to install again