Turn the top nut on the "IN" cable. This will tighten the cable and remove the slack. It's exactly the same way as tightening a bicycle brake cable. If you run out of threads and there is still slack, you can also adjust the nut on the chain. If there is still slack, you can stack a bunch of washers on that cable that has the slack between the nut and the blue "IN" catch. This will give you some more extension. It may take 15 or 20 of them them, but the other alternative, if the cable is stretched out, is to cut the cable shorter and re-crimp it. You'll need the tools to do that.
One set of cables is deliberately criss-crossed. It has to be this way in order for 4 cables to pull the slide in, and 4 other cables to pull the slide out. Don't flip that blue catch over, It has to stay in that position. Those cables tension just like a bicycle brake cable. No different.
2019 Montana High Country 375FL
2014 Chevy Duramax HD 6.6 - 3500 Diesel Dully Long bed Crew Cab