Of the three main ways to play the piano, solo piano is probably the most difficult. The reason is because you only have two hands, but you need to play all 3 elements (melody, chords, and bass notes). There are many ways to do this, which can be mixed and matched.
The best way to approach solo piano is to become very proficient with all the basic tools of music; scales, arpeggios, chords, rhythms, reading, etc., and then practice making up arrangements from melody and chord symbols with:
1. R.H.melody L.H.chords and then 2. R.H.chords L.H.bass 3. Then you’ll be ready to work on solo piano.
If you’re a beginner, you should learn several solo piano pieces before trying to make up your own arrangements. There is a vast amount of sheet music available with full grand staff arrangements for piano which will give you ideas that you can use for your own arrangements.
The basic idea is have the melody in your right hand be the highest note, and fill in notes from the chords under that. The left hand would commonly play roots in octaves or roots & 5ths or broken chords (1-5-10) or roots and 7ths. The left hand could also play walking bass or other bass parts, depending on the style of music.
It is common to practice one hand at a time and then both hands together.
Once you’ve got the basic tune, the next step would be to add fills and then practice improvising the melody line (take a solo).
The end goal is to be able to look at piece of music that has only the melody and chord symbols and be able to instantly make up an appropriate arrangement. Of course an arrangement can further develop over time.
For more information see my eBook “For Piano & Keyboard Players Only”