Increase Windows Partition Size - El Capitan

I have a late 2013 Macbook Pro Retina, and I'm looking to play games through Bootcamp. I already have a Windows partition with 30GB but need to increase the size to accommodate a game. With the new El Capitan update, I've read that I have to disable SIP in order to change the size of my Windows partition.

I still consider myself a noob when it comes to Mac software, but I would like to play a game I just got, Final Fantasy XIV. I'm hesitant to disable SIP as I don't know what exactly it will mean for my machine. Do you think it is safe to do so, and to increase my Windows partition to handle my download? Should I look into downloading the game to an external drive and playing it from there? I currently have Camptune X, which can resize the partition easily, but it asks that I either a) disable SIP or b) create a backup on an external USB. I don't have a Mac compatible external HD but am happy to get one if that is the safest route.

Just looking for advice as I don't want to make a mistake that I cannot fix. Thanks all and take care.