Bike maintenance is one of those things where you really do learn by doing. We all had to start somewhere.
Four years ago, when I got back into cycling after a fairly lengthy hiatus, I would never have dreamed of building a bike from scratch, and yet here I am, with an almost complete bicycle after finally biting the bullet.
Books and youtube vids have been covered comprehensively by other posters, but one thing I'll add to that, is if you are buying tools, it really does pay to buy decent ones. Whether that's something basic like allen keys or tyre levers or something more specific like a crank remover. Good quality tools that are right for the task in hand really do make life easier.
There is a knack to fitting tyres, though there are tyres and tyres. Some are a right pain to fit, while others will roll on just using your thumbs. Also, some tyre levers are better than others. I have a set of Wilkinsons ones and a set of the yellow Decathon ones. For all that both sets cost me near enough the same, I much prefer the ones from
Decathlon as they give me far better leverage.