How to get started with a GVP Spectrum 28/24?

[zipper]

I've always installed the card before the software, not sure if that would make a difference.

No, it won't - I have used different cards with same settings, just have to attach them to the particular board. And be sure they are not too high...

[zipper]

You also have to drag into the rightmost box (?) so it creates a new mode - by default it creates 640x480 256 colours mode. Then another which needs to be modified into Hicolor, third into Truecolor. Then again another, which must be first modified into 800x600, 256 colours. And another into 800x600, Hicolor etc etc. Takes lots of time.
You could download this to get some ready to use settings:
http://main.aminet.net/pub/aminet/driver/moni/P4_1438.lha