How to use Raspi2fb to get a larger resolution?

[kwouters1]

I'm trying to achieve the same as in this link: WouterJD/FortiusANT#311
The display is working at 480x320, and i've been able to install Raspi2fb.
But my LCD keeps showing the native resolution.
How do I get a 1024x768 resolution on my little LCD screen now?
Could anyone provide me with the right commands/settings?

[GewoonGijs]

@kwouters1 I have elaborated the solution in the original issue in FortiusAnt