Resources on how to solder

There are technical schools which teach basic electronics skills which would be your best bet.

Here's a good reference on iron tips which can be helpful Soldering Iron Tips

Searching the web I'm sure you can find YouTube vids that show the process.

But just like anything it's practice! To build the skills. Knowing what you are soldering from metallurgy of what you are soldering as well as the makeup of the solder its self, understanding how heat is moved and how heat is absorbed are all important elements. And lastly, understanding fluxes as well as prep and cleaning.