To start emacs, enter the command emacs, optionally followed by the name of the file you want to edit.
Under X Windows, emacs will open its own window, so you may want to run it in the background:
emacs myfile &If you would rather have emacs execute in the xterm window, type emacs -nw (stands for "no window").
Emacs contains its own tutorial, so there's no point in documenting it here. To start the tutorial, type Ctrl-h t. Type Ctrl-X Ctrl-C to exit emacs.