You can load data into matlab using the "load" command. The data should be arranged just as you would want to appear in the matrix; for example, loading a file which contained:
would result in a two row, three column matrix.
The file should end in the extension ".dat". To load the file into a variable in matlab, you'd type something of the following form (substituting the path for your data) at the matlab prompt:
The data from the file will be loaded into the variable "filename".