That plate just covers up the mount for a direct mount front derailleur. If your bike has a port for an internally routed dropper post it’ll probably be either on the downtube or near the bottom of the seat tube. The manufacturer’s website might have some info on where it is. If you’re running an external cable, your frame might not have routing for it, in which case you’d just use some straps, zip ties, or electrical tape to hold the cable in a few places. Just be careful that nothing pulls on it as you turn or your suspension sags.