Cannot push changes to github

In the terminal, I've given the following commands:
git remote add origin REPOSITORY_NAME
git branch -M master

when i try to push changes using git push -u origin, it said I've to enter git push --set-upstream origin master.
When i did, I got this error
error: src refspec master does not match any
error: failed to push some refs to 'REPOSITORY_NAME'

What is stopping me?
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