I can't recommend any particular resources, but yes it's called harmonization and I'm sure you can get started by searching "how to harmonize a melody." YouTube

I can't recommend any particular resources, but yes it's called harmonization and I'm sure you can get started by searching "how to harmonize a melody." YouTube has a billion videos on this sort of thing. You may also find it fun to play around with reharmonization, which is where you take an existing tune and find a new harmonization to match its melody.