Loftwings and Demons

Here are a few Krita tutorials online.  I watched the videos all the way through and skimmed through the articles, and these seem like a pretty solid introduction to Krita and what it can do.

Video Tutorials:
Krita Tutorial For Beginners
Krita Animation Tutorial: Coloring With the Fill Tool

Written Tutorials
Colorizing Line Art
Inking
Getting Started With Krita by David Revoy
Quick Krita Fill Tool Tip by unspeakablehorror

You can download Krita for free at https://krita.org/en/download/krita-desktop/.