Multiwire branch circuit question

Been lurking for a while, but finally found a question that I can't quite find an exact answer for.

During a recent remodel, I asked the electrician to run a couple circuits into the attached garage so i could add some outlets and lights (figuring maybe 4 outlets on one circuit 15amp, and a couple lights and an additional outlet or two on the other). I figured i do that myself to save some money. So I'm finally getting ready to start the project, and realized it's 14/3 coming into the box (black and red hots, white neutral, ground).

While i've done some simple electric work with one hot/one neutral, i'm not exactly sure what to do with the shared neutral. Is it as simple as wirenutting the neutral, so I'd just wire one run with black and the split neutral, and the other with the red and split neutral? Or do i just call the electrician back as this isn't something i should be messing with. As I passed electrical inspection from a thorough inspector, i'm fairly certain the wiring is all done correctly at the breaker box. Doesn't seem like it should be too hard, but I haven't been able to find the exact answer on fairly extensive searching.