I tipically use a matrix if I want multiple save "files" with each row or colum as a whole file. Lists are better for single save files, and they are simpler.
to access a cell in a matrix do this: (using matrix A)
Mat A[y,x] // y and x are coordinates in the matrix.
you can treat this just like a normal variable, anyplace you could put a number you can put this.
same goes with lists but the sentax is diffrent: (using list 1)
List 1[n] // n is the index number in the list
to create a matrix in a program do the folowing:
{r,c}->Dim Mat A // r is the number of rows and c is the number of colums
for lists it goes:
n->Dim List 1 // n is the number of cells
using the Dim function automatically sets all the cells in a matrix or list to 0, you have to fill them aftreward, this also means that you cannot have it Dim your save file every time you run the program because it would erase all the data. have an initalize option in the main menu to prevent this.
also remember that any thing you can do to one of the letter variables (A,B,C...r,o) you can do to a List or Mat, just make sure you dont try to access a place in the List/Mat that doesnt exist ( in a 10x10 Mat dont try Mat A[11,2]).
hope that helps.