From the specs, you can attach up to 8 line level outputs to amplifiers or to powered studio monitors (speaker with built-in amp). That gives you 4 stereo pairs of speakers, or 3 stereo pairs and a subwoofer if the speakers don't have enough low bass range for an organ, as they usually don't.
Line outs 1 - 4 on the back can be sent to 4 balanced amp inputs or powered speakers using four 1/4" TRS cables (amp end connectors either XLR or TRS), or to unbalanced amp inputs using 1/4" TS cables (amp end connectors usually RCA phono plug).
Headphone outs 5 - 8 on the front can be sent to 4 unbalanced amp inputs or powered speakers using two 1/4" TRS to RCA Y adapters to split the headphone signal into left and right. These signals will be lower level, so you'll be turning the amplifiers' gains up higher than the ones on line outs 1 - 4 to get equal volumes.
I'm ignoring the 2 channel SPDIF output because that's used more for hi-fi than live instruments.
I find powered ("active") studio monitors easier to work with, but people also use component amplifiers and unpowered speakers, except for the subwoofer which needs its own built-in amp.
Possible speaker examples: Adam Audio T8V, up to 4 pairs without subwoofer. Or T7V, up to 3 pairs with a 10" or 12" subwoofer. There are many brands and models. I have 4 models of speakers from Adam and KRK, and an SVS subwoofer. There are many discussions under Amplification in this forum.
If you're using surround organs, with front and rear mic perspectives, you'd place one pair of speakers behind you for the rear ranks and 1 - 3 pairs in front for the front ranks.
Please use google to look up the jargon I've used if you don't know it. You'll need a basic understanding before you spend money on this.