You have a lot to learn.
The drain hose, if I get this right, is the the drain for the sewer. The storage compartment is for carrying the hose while in route. You must hook it to a sewage dump to use it. The hose is like a "slinky" and will be much smaller when collapsed, and will not require 20 feet of storage space. You will also need a water hose, white one, and some electrical adapters and extensions, maybe. Most dealers include these in the purchase. Keep asking questions, we;ll help where we can. Sorry, it's a learning curve for everyone.
Basically, you are building a house each time you go camping. You have to look at the site, get the camper,(house), in to it it, level it, get it blocked and secured, get fresh water, electricity, and sewer, connected. It is fun, but takes time. Good luck.
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LadyWindrider
2012 Ford F250 ext. Cab 4x4
2002 Jeep Wrangler Sahara
2008 Yamaha V-Star 650 Classic
2008 Work and Play 18LT