You will find some pictures or video of removing the downpipe which basically involves disconnecting the catback in the UP/DP install sticky. But it really is that easy anyway. Just find the two bolts with the springs after your last stock cat and undo those, then pull it off the hangers. Also be sure to collect all the washers when you undo the springs, some stuff will want to launch. If you have a hard time threading on the spring bolt nuts when putting it on, take some large pliers around the bolt head and the opposite flange and squeeze bolt through the spring to put the nut on (probably unnecessary for you, I was using a huge donut gasket for a different downpipe).
You may want a new donut gasket and/or new spring bolts depending on the condition of yours (one of mine was very rusted and thankfully sheared off before I had to undo it all the way).