For this mod, you'd just have to place the files in the StardewValley/Content folder under the same folders they come zipped in (e.g. unzipped mod/Animals/ files go in your Content/Animals folder). Since there can only be one FarmAnimals.xnb file, to use multiple peoples' non-default animals, you'd have to edit the file yourself. You'd have to use xnb_node to decrypt and reencrypt the .xnb file into a filetype you can edit (just like how you have to unzip .zip files). Then you can open the extracted .yaml file in a text editor and add all the animals you want yourself (the animals from both mods). Since you're on a Mac, I'm not sure xnb_node will run for you since it uses the windows console. As far as I know, there's no Mac version of the game, so I'm guessing you're running it through a Windows emulator like Wine. You'd have to do something similar. Unfortunately, I don't have a Mac so I can't really help you there. I'd suggest Googling something like "how to run Windows batch files on Mac." As for editing the actual FarmAnimals .yaml file... You'll see a bunch of lines of text in the lower-half of the document. You'll see what I mean. They all look something like "White Chicken: "numbers/numbers/numbers" #!String." Copy and paste a new one of these lines (whichever corresponds to the type of animal you're trying to make), and change the animal name that appears before the colon to the name of your new breed. However, if you copy and paste the data line for a pig and try to use it for your new duck breed, you're going to get some weird behavior, but that's probably expected.