The best resource to learn the basics that I have seen is a "comic book" that was made about 15 years back [1].

It goes over the basics and helps you get going. From there I suggest reading posts, watching videos and just talking to people who solder. Find some bare board kits (or your own kits) and assemble them. Soldering, like welding, is one of those things you can learn to do in a day...but it takes experience to get good at it. A lot of what you do is by "feel".

Once you get a hang of it and would like to be able to inspect your own work find a copy of IPC-610A (there are free PDFs online often, otherwise it is expensive). This gives a visual representation of what is a failure or just a process indicator.

edit: Most important. Do not touch the solder to the iron tip. You heat the joint and touch the solder to that. This is the most common newbie mistake you see.

[1]https://mightyohm.com/files/soldercomic/FullSolderComic_EN.p...