El Capitan & Sims 3: Problem with Disk Utility

I'm not sure if this is more of a disk utility issue and therefore not something that y'all could help me with, but I wanted to try anyway. So I use the Mac guide for installing Sims 3 -- here -- and I've been having problems with step number 2.3. First of all they changed Disk Utility which really sucks. I go to make a New Image (cmd + N, Image > New) and then I've followed all the instructions. I name it, I change the size, and I set it to CD/DVD just as the instructions say. When it finishes being created, it always says that it's only 500 MB or 1.5 GB in size, no matter if I made it 5.6 GB when I first created it. I've tried moving the files over just in case, and it always says that the Image is too small. I've even tried making it only 2 GB, and it still always says 500 MB. Heck, I even tried putting 2,000 MB. 

I have no idea if I'm just doing something wrong, if the new DU just sucks, or a mixture of the two. 

Any and all suggestions will be greatly appreciated! Thanks. (((: