How do I track, pull, etc. from an existing git branch on Github

How do I track, pull, etc. from an existing git branch on Github

I have the master branch from a repository on Github cloned on my machine.
There are other existing branches in this repository that I would like to
be able to switch to and use. I'm trying to use the command:
git branch --track nameOfBranch origin/nameOfBranch
This isn't working for me. I get the error:
error: the requested upstream branch (URL) does not exist
Basically I need to create the branch on my local machine and tie it to an
existing branch. Thank you for your help!