All the tutorials and the manual on hinting seem to be for the older version of Glyphs, The panel where you add the vertical and horizontal numbers is not the same in G3.
Under stems it’s not totally clear what to do, I added a new item called Horizontal Stem but it seems to only accept one value?
Can you point me in the right direction
Many thanks
I was just coming here to ask the same question. Hoping someone can give us an answer 
What numbers where you referring to?
There are two parameters, the TTFStems and TTFZones. Both are only needed if you need different values that you have defined for the postscript hinting. The setup is rather self explanatory (I hope).
Do you have further questions?