The Beastman of Farum Azula can be found in the Groveside Cave in Elden Ring, and is an optional boss you can face early on.
Defeating it will drop a useful item for your adventure, as well as the cave in general being a decent place to farm up Runes.
Here's what you'll need to do to beat it.
Preparation
If you don't feel too confident in your early-game strength, you can continue past this boss and on to the Site of Lost Grace. Here's you'll meet Melina, and unlock the ability to level up your character using Runes you've collected. Naturally this will make you stronger for taking on the boss.
A better option, however, is to farm Runes by doing the tutorial and killing animals and soldiers around the Church of Elleh. Then, buy the Noble Sorceror Ashes and/or Lone Wolf Ashes from Merchant Kalé inside the Church. You'll be able to summon these at the start of the Beastman fight, making it easier.
If you're not playing a spellcaster, converting all of your Flasks to Flasks of Crimson Tears is a good idea. You'll need the healing potential through this fight if you're not levelled up much.
Combat
The Beastman of Farum Azula is a pretty basic fight, given its appearance early in the game. Using melee attacks, it'll come at you aggressively, with extensive combos. There are several ways to handle the creature.
If you've gone with a spellcasting class, keep your distance. Perform backwards rolls between spells to keep this distance up.
If you're the Warrior, you'll need to opt for a hit-and-run tactic -- attacking, then dodging and trying to position yourself behind the creature. This is also the strategy used when you need to recover health or stamina.
Two-handed weapons and special abilities will deal massive damage, and give you the opportunity to chain attacks together. Remember to move away before you run out of stamina, or you'll feel the brunt of its counterattack.
Rewards
As well as a decent number of Runes, you'll earn the Viridian Amber Medallion for your efforts.
It raises your Stamina by five points, which is nothing to be sneered at early in the game. It'll likely be your first Talisman too, meaning it will see use until you can replace it.
The real rewards, however, are found in the chest nearby. The Flask of Wondrous Physick allows you to create consumables with different effects once mixed with Crystal Tears at a Site of Lost Grace.
You'll find a Ruptured Crystal Tear and a Greenspill Crystal Tear in the same chest. The former creates an explosion, while the latter increases max Stamina temporarily.
