For this type of error you should just update the existing remote using:
$ git remote set-url origin [email protected]:ppreyer/first_app.git
As the error message indicates, there is already a remote configured with the same name. So you can either add the new remote with a different name:
To add a new remote, for example, github instead of origin, do the following:
$ git remote add github [email protected]:ppreyer/first_app.git
While pushing you should use
git push github master
Thus, you can resolve this issue by creating a new remote with a different name instead of origin.