Save SSMSToolsPackLicense.xml to either of the following two locations (C:\ assumed as system drive):

Per machine location (preffered, visible to all users)
     SSMS 2012: C:\Program Files (x86)\SSMS Tools Pack\SSMS Tools Pack 2012\
     SSMS 2014: C:\Program Files (x86)\SSMS Tools Pack\SSMS Tools Pack 2014\
     SSMS 2016: C:\Program Files (x86)\SSMS Tools Pack\SSMS Tools Pack 2016\
     SSMS 17: C:\Program Files (x86)\SSMS Tools Pack\SSMS Tools Pack 2017\
     SSMS 18: C:\Program Files (x86)\SSMS Tools Pack\SSMS Tools Pack 2019\

Per user location (visible to current user only)
     C:\Users\{user}\AppData\Roaming\SSMSToolsPack\