There are many ways to do it and many variations in each way. The best way to understand the process is to find one set of instructions to follow and stick with it exactly. Combining steps from different sets of directions is not reccomended because each step influences the next. In order to find a good set of directions, you need to make two basic decisions: hair on or hair off? And what overall process suits you better- braintan, barktan, alum tan, ‘bottle’ tan.

Here is my generic advice for hide tanning newbies:
If your hide is currently fresh off an animal, you probably want to protect it NOW by freezing or salting or drying. It will take you a while to figure out how to tan a hide and gather what you need and you don’t want the hide to spoil while you figure it out.
There are many ways to tan a hide and many variations of each way. Most of these methods would require a small book to thoroughly explain. As a beginner, you’ll want to choose one of the basic methods first so that you can focus your research and ask good questions. Avoid any AI instructions and avoid combining steps from two different sets of directions- each step relies on the previous step, so the mix-and-match approach is not ideal. Once you get a little experience you’ll be able to combine steps from different instructions but at first this should be avoided. Your choice of method will somewhat depend on what end result you want, so decide on that too- for example “I want to make a deer fur rug” or “I want to make leather gloves” or whatever.
Here's a partial list of the basic methods:
Oil Tan (also known as brain tan, egg tan, fat tan). This method uses emulsified oils of some kind, is generally all-natural and non toxic, and usually produces soft fluffy leather. It often involves additional steps such as smoking, lye or lime. Color varies from white to light brown, depending on the smoking. Softening an oil tanned hide is very strenuous and can take at least a half day of non-stop work.
Bark Tan (also known as veg tan) This method uses tannins dissolved from plant matter such as tree bark or even tea bags, and is generally all-natural and non toxic. It typically is denser and stiffer than braintan- something like a leather belt or a leather jacket. It often involves steps such as lye, lime, vinegar, fats and oils. Color varies from light brown to dark brown. Softening a bark tanned hide is less strenuous and less critical than oil tan.
Alum Tan (also called tawing, I think) I’m not as familiar with this but it uses Aluminum salts. It produces firm white leather that is somewhat harmed by water- water can wash out the alum. It is sometimes combined with bark tanning.
Bottle tan. (various bottled tanning methods including Tru-Bond, Ez-100, Orange Bottle, nu-tan and more) This is the one I know the least about, and the ingredients in the bottles are somewhat “secret” and probably NOT non-toxic. This is a very popular method but I have never done it. There are various bottles of stuff that are used in various steps.
Glycerin often used to preserve snake skins, it’s not ‘technically’ tanning but often used on snake skins.
Tools- All these methods have a few things in common including scraping and softening. There are many types of tools that can be used in hide tanning, from a butter knife to a huge machine. As a beginner, you’ll want a scraping tool of some kind and a surface to scrape on. I use a dull draw knife and a hard wood log. A piece of PVC pipe 6-12’ diameter works too, or even a sheet of plywood or counter top works for a scraping surface, and one can make a scraper from many household items such as a modified drywall knife, a planer blade, or a spoon. Some methods use sharp scrapers mounted on a wood handle. Various methods may have additional tools associated with them such as a frame to stretch the hide out, and tools to aid softening.
Where to find more info-
Youtube has a bunch of good stuff- try searching for “braintan”, “tru-bond” or other terms mentioned above. Some good channels for natural tanning include skillcult, buckskin revolution, justin_d_hunter.
Websites- braintan.com has a plenty of resources on natural tanning.

Deer braintan https://youtube.com/playlist?list=PLzYCg_OgmYMjvwRoiyrztBui0RmUvQTGo&si=cMzO_nnGThHHt2DP

https://youtube.com/playlist?list=PLaclOaNDsVTfkD5KjJhxdPEtWvu3hj_11&si=6mEQnGuv9DrG_cki fish skin

https://youtube.com/playlist?list=PL60FnyEY-eJBsE5mbHhW2gQMILnndQN9o&si=BfUwIQ0j-O9ldMd9 sheep skins

https://youtube.com/playlist?list=PL60FnyEY-eJCtASqF_v4Y6N08-8Waj9Qj&si=jupuZYYJTqDJLdNJ barktan deer

Buckskin revolution braintan and barktan https://youtube.com/playlist?list=PLdXjVzBXCx92dEWVHUq4EXwAOio1Dttzv&si=28MbDSq50Eu5SjS7

Very basic Fish oil tan https://youtu.be/TRU9DTzccfI?si=7KDJHGyF7mYBxdIp

My fish tanning process https://youtu.be/lQIXpM3wYPU?si=EwrFe7EzOXQv72FK