First run the following command:
$ git config credential.helper store
All you need to do now is pull.
$ git pull
Now you have to provide a username and password, remember that these details will then be remembered later.
Note that this will store your username and password in a plain text file at ~/.git-credentials. Anyone can open it and read it.
For better understanding about these commands go through the following crash course on git that will help you to understand git well