To input a matrice with prompt, simply use ':Prompt [A]' or [B] etc… It needs to be inputted as:
Where there are y rows and x columns.
It must begin with brackets, and each row must be inputted in brackets, then in list syntax with commas separating items. It technically needs end brackets at the end of the last row and the end of the matrix, but in TI-BASIC, they are not required. There must be exactly the same number of items in each row.
I don't think they can be inputted with the Input command.
Without the matrix input, matrices can be created on the homescreen in the same way. They must be defined in that way if you create it within the program.
Much as you can define a list in the program:
You can define a matrix as well.
They must be in that Syntax.
Because of this very strict syntax, and that it takes up a lot of time and space, I do not use matrices often when programming nor do I suggest them; I use multiple lists instead. The only real advantage that I can think of for matrices would be when making math programs with matrices, and when using the same operation on multiple variables. But if you must use them, go ahead.