Hey there!
Here's how to install the Legendary Markings v4.1 pack.
Step 1: Install the Legendary Markings v4.1 pack and open the folder once it's finished downloading.
Step 2: In your folder, you should see another folder called "media". What you want to do is open up media, textures, and then markings.
Step 3: Copy every single file that's in the folder and paste it into FeralHeart > media > textures > markings.
Step 4: Now that you have your new markings where it's supposed to go, look back at your Legendary Markings folder and there should be a .cfg file called markings.cfg. Go ahead and copy and paste it into your main FeralHeart folder.
After that, you should be all set! Reopen FeralHeart.exe and check out if you have more markings than you had beforehand. Let me know if this worked or not!