Im not a beginner, but my first recommendation would be to get a good teacher/ mentor. Tell them exactly what your goals are and be prepared to work hard. If a teacher is not optional, below are some things to get you started.
Things you want to learn as an absolute beginner (learning to play by ear):
- Name of the notes on the keyboard (12 notes)
- whole step and half step
- major scales (12 of them, well technically 15)
- major, minor, diminished triads ( 12 of each = total of 36 chords) btw, a chord is when you press at least 3 notes at the same time
This should get you started. These are simply tools that will help you to play songs.