Stackoverflow is great, google will often take you there because someone has already asked your question, and someone else has answered, usually many people have answered your question many ways.
Daniell Navarro recently made this website for introducing R, it’s great, check it out (also made using this R markdown process): http://compcogscisydney.org/psyr/
This is the definitive guide for all things R Markdown (you will find this very useful as you get better at this skill): https://bookdown.org/yihui/rmarkdown/