Most people should download the full install that includes the client, QuakeSpy, and QPlug. If you already have the latest QuakeSpy or for some strange reason don't want it, download the client only install. If you downloaded the client only for Windows or Linux just unarchive the package into your quake directory. When you first run QuakeSpy it will ask you to create a player profile for yourself. A player profile lets you set common options about how you look in the game, and what options you'd like to use.
Lets look at the player profile window and run through the options.
Select the pants color you like. Also turns off display of skins other than the default Quake skin while in the game. Setting them to Super Nail Gun means you would never automatically start using a grenade launcher, rocket launcher or thunderbolt when picked up. An integral part of QuakeWorld are the master servers. These are systems that act as databases of available servers to be used.