I started handloading by watching dozens of hours of YouTube videos and reading several reloading handbooks. In some areas there are classes taught that are an introduction to handloading but not many places have them. One way to start is to befriend someone who handloads and ask them to be your mentor. There is a lot of good information here on CGN but there is also a lot of bad information as well. Until you get to a certain point in terms of knowledge it can be really difficult to tell the difference.
Some good YouTube users for reloading videos:
Iraqveteran8888 (a tad abrasive sometimes but quite knowledgeable)
AmmoSmith Reloading
Gavintoobe
The Ammo Channel (often more esoteric stuff like casting)
To start off I'd get at least 2 different reloading manuals of the most recent edition and read them cover to cover (okay, I say that but you don't need to read all the load data in detail). You can order them from Amazon even. The major brands are Speer, Lyman, Hornady, Lee, Barnes, and some others. Most of the companies that write reloading manuals also sell component bullets (projectiles) for reloading so you can look around for those. Another book that I found quite usefull was "The ABC's of Reloading". It doesn't go too in depth into anything but is a good general introduction.