What I do when downloads come with only an installer and I want to install them manually, is install the files to a new, separate folder. I do this with some of my FeralHeart stuff just to make sure the installer isn't accidentally messing with any of my other files ^^ (I believe I did this for Feral City or another map map). While you are going through the installer, change the directory of where you want it to go. Once the installer is finished, just go to that folder where you had the files installed and copy and paste them into your FeralHeart game manually.
Let us know if you have any further questions about this!