At a command prompt in a terminal window, type M2. If Macaulay2 has been installed correctly on your machine, you should see a prompt such as this:
indigo% M2
Macaulay2, version 1.0
with packages: Classic, Elimination, LLLBases, PrimaryDecomposition,
SchurRings, TangentCone
i1 :
If this is the first time that you are running Macaulay2, then Macaulay2 creates a directory called .Macaulay2 in your home directory (on unix machines), or called Library/Application Support/Macaulay2 under MacOS X. Inside this directory are several files of interest, including an index.html file that contains links to your local copy of the Macaulay2 documentation.
The viewHelp command in Macaulay2 starts up your web browser (if it is not already running) and places you at this index.html page.
viewHelp
This web page includes links to the main Macaulay2 documentation, as well as documentation for any installed packages. This is a good time to bookmark the page in your browser.
At this point you should try something simple in Macaulay2, such as
printWidth = 60
R = QQ[a..d]
(a+b+c+d)^4
To exit Macaulay2, type one of: exit, end, quit, or your end of file character (which, under Unix, is often CONTROL-D).
exit
Macaulay2 can be run in this way from the command line, but it is generally much more convenient to run Macaulay2 from inside the emacs text editor. This is because you can more easily view larger objects, do command completion, use cut and paste, search, save your session, and so on. There is a nice mode for running Macaulay2 inside emacs.