Find a fox in a taiga, snowy taiga, or grove biome
Bring sweet berries or glow berries
Find two foxes if you want a baby fox
Sneak up on the foxes so they do not run away
Feed one sweet berry or glow berry to each fox
Wait for the foxes to breed
The baby fox will trust you and stay close to you
Use a lead to move the fox if needed
Keep the fox in a fenced area to prevent it from escaping