1. Obtain a github account if you don't already have one.
2. Fork the repo
3. Make changes to your fork
4. Raise the pull request

OK...

I already had a github account and have forked the repo, made the changes...

What's the right way to test it?
I've installed git but I've not used that for the PR. I've done it all online. The only file that needed changing was /Module/Starter/Somple.pm

I could just make the same change in my local copy installed from CPAN and test that. Although that would work for this simple change, it doesn't seem a good or scalable method of testing changes.

The common workflow is to create a fork, clone the repository to a working copy on your machine, make the changes, and run the tests (usually something like make test, or dzil test, etc.) For simple modules, prove -vl is often enough.
map{substr$_->[0],$_->[1]||0,1}[\*||{},3],[[]],[ref qr-1,-,-1],[{}],[sub{}^*ARGV,3]

The common workflow...

That makes perfect sense thanks

clone the repository to a working copy on your machine

This is where I get stuck...

I tried git clone module-starter but git couldn't find it.

Admittedly, I didn't try very hard as I ran out of time and I'm now away from my desktop where git is installed.