It’s as easy as fining one that you like, paying for it and arranging delivery.
From a dealer you will have the most selection and recourse and possibly a warranty.  However, from a dealer you will pay the most .
From an individual you will get the best price but usually only one piano to choose from.
Things to consider in buying a piano is…
The way it looks
The way it plays
The way it sounds
And price
If you like all four of those things then its probably the right piano for you but if one of those things you don’t like, it’s probably not the piano for you.