If you have cloned a remote git repository you default into a checkout of the master branch. Odds are there will be other remote branches, and usually one called 'develop'.
To start developing on this branch instead of the master, use the following command
$ git checkout -b develop origin/develop
> Branch develop set up to track remote branch develop from origin.
> Switched to a new branch 'develop'
This command creates a local branch tracking the remote develop branch and switches your working directory to this branch.
If you already have a local develop branch and want it to track the remote you can use this instead
$ git checkout develop
$ git branch --set-upstream develop origin/develop