There is no remote repository.
There only exist one repository on my local machine.
So here is what I did:
git branch new-branch
git checkout new-branch
//implemented some changes
//now wants to push changes to master
//what is the command?
As I Understand, what you are trying to do is "merge" your branch with master. so try the following.
git branch new-branch
git checkout new-branch
//implemented some changes
//to push chages to master first checkout to master
git checkout master
git merge new-branch