Thanks Jeremie. andreas_2 go on to your UE4 account and then 'my account' options, there you can input your GitHub account and link it.
Now for my new problem... Last night, I was able to see the substance plugin enabled in my plugin editor, so, happy enough, I turned off my computer. When I returned this morning the substance plugin is now gone. I opened Visual Studio 2013 and used 'Build Solution' again, (this worked). Is this something I will have to do every time I turn my PC on or did I simply forget to save something? But more to the point, I have a problem with importing my sbsar file - I drag and drop my sbsar into the content browser, it gives me import options, i proceed, i am prompted with the exact same window again, i proceed and then UE4 crashes.. Any idea why? Also just to make sure, what version of UE4 am I supposed to be running this on? 4.2.1, 4.1.2 or 4.0.2?
Again, any help would be great, thanks! Sorry for the hassle.