Learn all the main chords on piano and how to play chords in a song. For an introduction to my piano course go to:
https://youtu.be/WSqc2sJ9GJM
You get a: 1) PDF eBook which has piano chord rulers at the back to print out and use. 2) Examples as MP3 files that are stored in an archive file which can be unzipped on all computers.
Go to my website at http://markhansen.biz for some free piano video lessons to get you started.