You bought a medium to high end bike as a beginner, but whatever. If you can afford it, no problem!
I would buy this book and read it cover to cover so you know the basics of how things work and, if needed, how to maintain them. Your bike will eventually need maintenance, and learning the fundamentals of that make it less scary when something goes wrong.
Get basic safety gear (glasses, helmet, gloves), some appropriate riding clothes and shoes (you'll figure this out), and have fun.
Do your best to avoid upgrade-itis -- only replace things as they wear or demonstrate a real need to replace.
Don't go too big too fast (you don't need to start jumping big stuff, or absolutely flying through the woods on the edge of control) else you're way more at risk of getting hurt.
Don't store your bike outside (they aren't meant to take long-term exposure to the elements) and do basic cleaning stuff to keep it nice and it'll last.
And most importantly, have fun.
YouTube videos are only ok, I think. Often they leave out some steps that I needed explained in detail. If you can find it, watch videos made by parts companies, like Shimano, SRAM, etc. The book Zinn and the Art of Mountain Bike Maintenance and the Road version depending on what type of bike you get are invaluable. Also, a lot of trial and error. It’s good to have a LBS to help out when you’re in over your (my) head, like when I tried to adjust my derailleur.
Keep up the good work. Think of all the money you saved doing the work yourself. Sheldon Brown helped me through so many repairs. I also picked up the book from Leonard Zinn
https://www.amazon.com/Zinn-Art-Mountain-Bike-Maintenance/dp/1937715477
Youtube videos. Park Tools is the channel to start with. But GMBN and many others have good maintenance videos as well. Buy this book and spend some evenings reading up on various parts of your bike:
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https://www.amazon.com/Zinn-Art-Mountain-Bike-Maintenance/dp/1937715477/
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If you are really interested in learning, buy an old cheap "project" bike off somewhere like Craigslist and work to tear it down and build it back up again.
I would recommend snagging a copy of "Zinn and the Art of MTB Maintenance," it's a fantastic guide that will walk you through everything you need to know!
https://www.amazon.com/Zinn-Art-Mountain-Bike-Maintenance/dp/1937715477/
I would also suggest checking with your local bike shop or cycling club if you have one, they often (pre-pandemic at least) offer "bike maintenance 101" classes where they'll teach you how to fix a flat, tweak your shifters, and get everything ready for a ride.
Changing tubes and tires is definitely do-able for a beginner! I think everybody should know how to replace a tube in case you get a flat while out riding. Swapping out brake pads is also a pretty easy fix.
For bike parts, you'll probably want to avoid the no-name-made-in-China parts that you might order off Amazon, but if you order from your local bike shop or an online bike retailer, pretty much anything you get should be decent quality!
Everyone (for their best protection) have to know the basics:
https://www.amazon.com/gp/product/1937715477/
First thing I bought when I got my e-MTB.
Aside from YouTube, this is a great book to have in your garage Zinn & the Art of Mountain Bike Maintenance: The World's Best-Selling Guide to Mountain Bike Repair https://www.amazon.com/dp/1937715477/ref=cm_sw_r_cp_api_i_3H0D28N5ETX7GTADABVQ
Not mountain bike specialists, but Bike for Good, Willy Bain and Billy Bilsland Cycles are all long established bike mechanics with a good reputation. I've used all three in the past for servicing and repairs and found them all to have fair prices and good assessment of what work needs done.
They will, however, all be extremely busy due to the boom in cycling that has happened recently because of COVID19, so you might need to wait a few weeks for a slot in the schedule.
If you fancy learning to fix up your own bike then <em>Zinn and the Art of Mountain Bike Maintenance</em> is pretty encyclopaedic (there is a road bike version too). You can do a fair bit with quite basic tools and if you need something more specialised, then Bike for Good will let you rent a workstand by the hour and use their tools (although I'm not sure if this is restricted due to COVID).
Also /r/bikewrench is a good place to ask questions if trying to fix something.
Also buy this book, so you don’t waist money on simple repairs.
Zinn & the Art of Mountain Bike Maintenance: The World's Best-Selling Guide to Mountain Bike Repair https://www.amazon.com/dp/1937715477/ref=cm_sw_r_cp_api_i_pckpCbJ56KVJX