Slightly OT

[Roger]

I'm using Fedora 19 developing a couple of small Rails4 apps.
A friend who does php programing has offered to help me complete the 
coding . He is using winxp because he had to much trouble getting Rails4 
and Ruby2 working on Fedora 16 in a virtual machine at his work.

I have the master app on github and pushed to heroku where it works ok.
I have no knowledge of github or heroku other than that.

For me alone I have been working on the master app in my home directory 
and pushing frequently.

My questions are.
What is the best way to allow him to work/collaborate on the project and 
push to both github and heroku.
Should I create a branch or a fork on github? and/or heroku?, what is 
the difference between branch and fork?

I have googled and read both the github and heroku help but am very lost 
when it comes to understanding what is the best way to handle this.

Help would be greatly appreciated thank you.
Apologies for so off topic.
Roger