To learn piano by ear is one methods among others. People who are born blind in the past could only learn this way.
1. Orientation on the keyboard:
First you have to learn the pattern of the black and white keys and find the octaves. You should do this like you were blind, but of course you can control it with your eyes.
Likes this you will also learn the names of the scales and recognize the triads and chords like major, manor, diminished. Listen carefully to the different sound and the impression they evoke.
Play the chord progression I-IV-V-I in C major: that means the triads of the degrees C, F, G. Play the Bass notes with the left hand and the triads with the right hand. Now you can already play your "1. symphony op 1" in C. Play the same chords in other sequences like I-V-V-I IV-I-V-I etc. By changing the time and rhythm in 3/4 you can play your first Waltz (Opus 2).
You are now already able to accompany yourself singing some songs or a friend playing another instrument.
Look up the Blues pattern: you can play it also with these 3 chords:
(last bar will be G to repeat the whole progression)
Play the same progression using tetrads as minor 7 chords with the r. hand:
by adding to the triads the 7th: C7 = C,E,G,Bb F7 = F,A,C,Eb G7 = G,B,D,F
Learn the Roman number for this progression Ib7, IVb7, V7
One of the most used patterns is the progression I,vi,ii,V (also with the 7)
which is C,a7,d7,G7 (note capital letters mean major, a7 = a minor, also written as Am.
Play the progression VI V IV III (or in the parallel minor scale i,VII,VI,v
in C major this will be am, G, F, em
3. Scales and keys - Circle of fifths:
The next you'll have to do is learning the other scales and keys:
Start with G major scale up and F major scale down. You will find out that you always have to add a # or a flat. Play the chords and degrees, the patterns you have learnt in C-major in these other keys.
You will develop yourself the circle of fifths and if not you can look it up.
You'll find out that you can use the V7 of G7 also in your songs you've played in
C like e.g.: C,C,F,F,C,C,C,C,F,F,C,C,D7,D7,G7,G7,
You will do these exercises also playing the inversions of all triads in the right hand, and also playing the whole chord accompaniment with the left hand alone.
First only triads in root position, later the Bass note on the first beat and the upper chord tones on the beats 2,3,4 or 2,3, when playing a Waltz.
This means you don't play the full chord at once but like picking on a Guitar or Harp
you play each note after the other up and down:
left h.:c,e,g,e or c,g,e,g or l.h.c, r.h. e,g,c,e,g,c,e
In a 6/8 time this will be r.h. e,g,c,g,e etc. together with the root tone in the l.h.
4. Play the songs you know:
Now will be longing to play a song!
(I hope you did long ago - in exercise 1.)
Here are some titles you can start with:
Joyful, joyful (Beethoven Symph. 9)
This old House
O when the saints
Good night ladies
What shall we do with the drunken sailor
A groovy kind of love (Phil Collins)
I can feel it in the air tonight
Another day in Paradise
Lady in black
Several songs by Michael Jackson and the Beatles are quite easy to play by chords
and singing the melody.
try out also Rock'n roll, Blues and Boogie (Bass-riffs and melody licks)
The house of the rising sun
Well - I wish you a merry Christmas and hope you start playing not only by ear!
You will have much more success if you are not a musical illiterate!
To explain and read these exercises above you need only 5 - 10 minutes but to understand them and being able to apply them might need you months and years! My advice is to learn sight reading and my personal recipe is: reading by writing! This means notate everything I've told you here in numbers (1,3,5), Arabic letters (c,e,g), Roman numbers (I-III-IV-V), writing lead- sheets and drawing the keyboard patterns of new chords you're learn together with the notation in a staff system).
There are lots of good questions here about sight reading and many helpful answers. Look them up and look up all bold written titles (tags) above.