Re: New PCgen user... how to add sources?
The only 35e WotC sources that I'm aware of is Bahumets Github repo.
And downloading is just like any Github repo. And he has instructions.
On the front page of any repo there is a button on the right labeled Clone or Download. Click that and select download zip. Then unzip that and erop the contents of the pcgen folder into your pcgen folder on your computer.
Note that his files aren't fully compatible with the base pcgen files i believe.