As a guitarist who also does some beatmaking/computer music production myself, I understand where you are coming from. I'm not a drummer, so I can't really offer solid theory per se, but I can give you some advice to get started.
Listening to beats in songs you like is a great place to start. Listen for the kick drum, snare drum, and hi-hats. For rock, pop, hip-hop, jazz, blues, and any genres that use a drum kit, those are the three main components that make up a beat. Even newer EDM type stuff is based on those three drums, with some variations thrown in.
Depending on which software you use I have found Youtube to be a pretty good resource for this kind of thing as well. For a more specific details, let me know what software you are using and what music genre you are aiming for.
Quick tip: Snare on beats 2 and 4, bass/kick drum on 1 and 3, and hihats on eighth-notes is the standard starting place for most rock/pop drumbeats. You'll recognize it once you hear it.
A couple ones I have found helpful on Youtube:
they both offer paid classes, but they have a lot of free content up on Youtube as well. I really can't overstate the usefulness of Youtube in this siutation.
Edit 2 after comment:
I use Ableton Live which uses more of a grid-based approach, where you either play the keyboard or just draw in the notes one-by one on a rhythm grid. But in general, in hard rock or metal, its the same general beat I described, but usually they just do more with the bass/kick drum. In metal especially there is a lot of fast kick drumming, where they use two foot pedals or even two kick drums to punch out the rhythm in 1/8th notes, 16ths, or even 1/32 notes. Also they hit the snare on beats 2 and 4 as usual, and instead of a hi-hat they will ride the 1/8 notes on cymbals for a heavier sound. (standard rock example with fills / metal example / hard rock example with more kick/snare variations) Of course on top of the standard beat they will throw in fills that include more cymbals and the toms, but those are usually just variations used between sections and require more complex patterns and explanations.
From what I can tell, Ez Drummer uses a different approach where it has a lot of built in beats and loops that you play around with to find a combination you like. I don't see much about programming in beats yourself, and although I'm sure thats possible, for your purposes it seems more like you can just mix and match with the presets they have built in.
Again, with this type of thing its much easier to SHOW you than TELL you, so here are a couple examples:
And more where that came from: