1. Install the connection box. This plastic box sells for around $20 and it has the hot/cold valves where you connect the washing machine. The center knock-out is where we'll connect the 2" drain pipe. It's supposed to be installed higher than the washing machine, not less than around 34" high. Mine ended up around 38" off the floor.
Typically, you'll be joining your supply lines to existing pipes somewhere under the house. You might consider adding some valves when you do this. Valves are always quite handy, especially in older homes where there are none to be found!
TIP: Take out a Sharpie-type marker and label your PEX "hot" or "cold" with arrows so that you (and others) will know what's going through each pipe. It may be extremely helpful later.
3. The drain may be trickier to install depending on where you have to connect to. If you're unsure, always call a plumber because this isn't something you want to guess about or you'll have a pond to deal with. Thankfully, my connections were just behind the block wall where the washer/dryer were located so I didn't have far to go. Usually, your drain pipe will just go straight down and join with a P-trap that is just under the floor before going on to connect with the system.
You can see mine in the picture. I actually made two cuts to fit the flexible "T" in place. It was a little messy, but actually went pretty quick.









After sanding and clean up, I started laying baseboard. Old homes like this Inglewood house from the 1920's often just have simple wide boards as a base. The existing ones were 7" tall so I had to buy a 1x8 and rip it to the right width to match. 


They say that this type of roll roofing should last 10 years. Even still, you'll want to keep an eye on any flat roof. They are notorious for good reason.
After some discussion we decided to go ahead and 
