Start with the Matlab Help window that you can open from
the main window by choosing Help menu, Overview....
There are two sections in the popup-menu Topics in the Help window,
OVERVIEW and GETTING STARTED. Execute
the instructions in GETTING STARTED in order to import
a signal sig1 (sampled
with Fs and see it and its spectrum.
With the Help menu, Context Sensitive... in the main GUI, you can click any object in the main GUI to see more information.