To to a large extent, once you have downloaded MacTeX itself you will not need to install any packages except to keep your distribution up-to-date, and for this you use TeX Live Utility.
What TeX Live Utility is for
TeX Live Utility is not a general purpose package installer, but a tool to manage an existing TeX Live distribution (in your case, MacTeX). It provides a graphical user interface to a subset of the functions that the command line
tlmgr can perform. Specifically, it can do the following things:
- Update your existing packages to the latest versions on CTAN.
- Install any new packages that have appeared on CTAN since the last update.
- Change the global paper size for your distribution.
Basic use is really simple: open the application (if you have installed MacTeX it will be found in the TeX folder inside your Applications folder). When you do this you should see a window that looks like this: (the URL field in your window will be different from this one.)
From here, you should usually choose Update All Packages from the Actions menu. You should do this immediately upon installing MacTeX for the first time, and then periodically thereafter.
Items in blue are new packages that don't yet exist in your distribution. Items in black are existing packages with updates available.
If you don't want to update or install everything, you can select particular items from the list with the mouse and then choose Update Selected Packages. (Unless you know what you're doing, this is usually not the best option.)
Since MacTeX is installed using administrator permissions, you will also need to authenticate using an administrator account to update your distribution with TeX Live Utility.
Sometimes you will see the following message:
and the installer itself will update first.
One other thing to understand is that TeXLive operates on a yearly distribution system, and by default the TL Utility will only update the current year's distribution. For example, since TL 2015 has been released, but I have not yet installed it, I can no longer run TL Utility in its default mode, and receive the following message:
What TeX Live Utility is *not* for