First you'll need to install
SMAPI if you don't. There is a whole guide on how to install this one
on the wiki.
Alright, after you get SMAPI, then it is time to install the BFAV. Everything now goes on
Stardew Valley/Mods folder, and it will depend on which version you got: gog, steam or mobile, so for this one please refer to the wiki, right under the SMAPI tutorial.
I play it on the computer, so I can't help with the android version
Download: https://www.nexusmods.com/stardewvalley/mods/3296
This is the main file. It has been "abandoned" for a while, so you won't be able to get assistance from the mod author but you can always get some help here on this forum. Anyway, after downloading and unzipping it in your mods folder, go and grab the unofficial update.
Download: https://forums.stardewvalley.net/threads/unofficial-mod-updates.2096/page-68#post-47274
Unzip it over your original mod and you are golden. One of the conveniences of this update is that besides fixing a few bugs and updating for the newer version of SDV is that you don't need to manually add the animals. Pretty neat, huh?
Some animals have custom products, so you might need to download and install
Content Patcher and
JSON for custom new objects. Please keep in mind that if you have your game set to any language other than English there won't be any custom product (unless you get the translation)
Now all you need to do is to go to your favorite mod hosting service and search for BFAV and pick whichever you want.
A few that I got:
I personally like putting a [BFAV] in the folder's name to keep things more organized.
View attachment 11687
(shown: parrots and canaries. They don't have custom products)