I'm not familiar with that particular Ibanez model, but I have an SR series bass with what I suspect is the same control configuration. With the way your pic is laid out, the controls are likely:
Top= master volume
Left= Pickup blend
Right=High band EQ control
Bottom=low band EQ control
If my suspicion is correct, there should be a center detent on all the controls except the master volume. You should be able to verify this with a little knob tweaking.
A good place to start with addressing your tonal need would be with the volume at max, and all the other knobs centered (i.e. both pickups full on and EQ flat). From there you can cut highs (ccw from center) and/or boost lows (cw from center). Also, favoring the neck pickup should give you a more bottom heavy sound vs favoring the bridge pickup, which should give more definition and growliness.
Inconnu mentioned that if the low band of the EQ were boosting low mids more than the deep lows, you might even want to cut the lows a little. I think that's good advice, but if the EQ section on yours is similar to my Ibby's, it should be a shelving EQ that will boost the lowest lows the most (my Ibby is from 1992 though, so they could easily be different). In any case though, I'd most recommend starting by cutting the highs. For EQ-ing to get better tonal balance, I'd generally recommend cutting freqs you have too much of before boosting freqs you want to hear more of. But, sometimes you need to boost too. Hope all that's somewhat helpful.