How to Connect Two Computers to One Monitor
1). Buy a switch box. Think about buying a box with extra ports in case you might want to hook up any extra machines later on down the line.
2). Buy a pair of SVGA cables if they aren't included with the switch box you buy (kits including a box and cables are a more practical value for most setups).
3). Buy any necessary adapters if you plan to connect a PC and a Mac to one monitor.
4). Shut down both computers.
5). Connect the monitor to the switch box (probably to the center socket on most boxes).
6). Connect both computers to the switch box (probably to the center socket on most boxes).
7). Connect both computers to the switch box.
8). Tighten all hand-screws on monitor plugs.
9). Turn on monitor.
10). Reboot both computers.
11). Turn the switch box from A to B (or whatever designation the box uses) to make your different computers appear on the monitor.