Paint help for the new guy

I’ve been lurking here for the past year. I’ve read the Horus heresy series and decided I want to play the tabletop, specifically chaos space marines, because the loyalists are just boring. My favorite legion is the emo hazard iron boys. I’ve bought a starter set between tyranids and the Smurf boys. Any suggestions on how to convert the Smurfs to iron warriors? Where should I go to learn how to paint correctly? I’m not a perfectionist, but I want to do a good job and would love your advice. Thank you in advance. Also what’s a good resource to learn how to play them on the table top?