On my '13: Remove the seat belt anchors (14mm bolts). Remove the 2nd row sill trim - one small (10 mm and large Phillips) bolt with a trim cover over in in the flat step area, the rest is held by clips and pries up. (If you're running wire front to back, you'll also probably also want to remove the front row sill on whichever side you are running it - no fasteners, they just have plastic clips). Remove the hooks in the rearmost side walls (quarter turn), remove the bolt behind them (large Phillips). Pry up and remove he hinged section between the cargo area and tailgate (just plastic clips). Remove the two pushpin fasteners - one on either end that were exposed when you removed that piece (they are in the bottom of the cargo trim). Take out the removable panel (holds a first aid kit on some). I think your 18 has automatic hatch and seat release? If so, I can't help with that part - my '13 had lever handles that needed to come out both sides (trim cover, bolt, undo clips). Then you can start prying the big panels - they are only held on by plastic clips. Just as you start, you will need to unplug electrical connectors - mine had one on the passenger side (temp sensor) and two on the driver side (temp sensor and power plug). The rest of the large panels just pry out by popping it out of the trim clips.
Here are what the clips look like:
View attachment 2351149
Trim tools can help a lot with popping the plastic fasteners. I'm not endorsing this brand (I have another brand), but these kinds of tools:
Amazon product ASIN B07L6F1D6Z