1. Hold food in your hotbar — every pokemon has a favourite: most love Berries, Charmander loves Raw Meat. Check the green bar above one to see if it can be befriended.
2. Look at the pokemon and press F to throw the food. Each hit fills its green friendship bar.
3. When the bar is full the pokemon joins you, gets a nickname, and fights beside you.
4. G makes partners follow / stay, T calls them back. Haunter and Magnemite can't be befriended — and don't hit a pokemon you're befriending, it gets spooked and runs.