Try this out:
Open up your "My Presets" folder first. It's located in your main Feral Heart folder.
When you open up your "My Presets" folder you should see a bunch of other folders inside it numbering from Preset_1 - Preset_12 & a reference file.
Say your preset download number is 8 like the one in my pic that I circled in red you will want to put it's contents into the Preset_8 folder. So copy all the contents from the download like so:
Then paste them into your "Preset_8" folder or whatever correct folder number matches your preset download's number.
Once you've done that start up Feral Heart and on the main menu type in your username & password as usual but do not click "log in" instead click where it says "tools".
After that click "Preset Maker"
Then from there click on your preset name in the box on the right and then hit "export".
If these steps are followed correctly you can then log in on the main menu into the regular character creator and put on your preset in the "V" option.