Execute a script after transactional replication setup completes
I need assistance to execute/run automatically below .SQL file/Query
  automatically at subscriber once publication is done


You should use sp_addscriptexec tsql to run sql script on all subscribers of a publication once the snapshot is applied to subscribers. Make sure you use @skiperror = 0 to stop the distribution agent when an error is encountered.

Brandon Williams has a good blog post on - Executing scripts with sp_addscriptexec