After following the below instructions, i was able to create a mirror in my GitHub account. But after that how to take update from the source repository.
https://help.github.com/en/articles/duplicating-a-repository#mirroring-a-repository
Open Git Bash.
Create a bare clone of the repository.
$ git clone --bare https://github.com/exampleuser/old-repository.git Mirror-push to the new repository.
$ cd old-repository.git $ git push --mirror https://github.com/exampleuser/new-repository.git Remove the temporary local repository you created in step 1.
$ cd .. $ rm -rf old-repository.git
Repeating the same bare clone and mirror push would update the repository from source.
You can employ the same steps each time you'd like to update your mirror: https://help.github.com/en/articles/duplicating-a-repository#mirroring-a-repository