To address a fixture which has DIP Switches, take a look at the Binary Addressing page. For fixtures with rotary switches or LCDs consult the user manual to find out the specifics of that particular fixture.
DMX addresses are 9 bits in length giving a total of 512 addresses and each address can have a value between 0 and 255, this block of 512 addresses is the most that can travel down a single cable and are known as a universe. If more channels/addresses are needed then another universe has to be added, which travels along it's own cable (one exception to this being the Pearl, where some of the five pin outputs feature a second universe on pins 4 and 5).
The term Patching refers to assigning control channels to DMX addresses, both at the console (transmitting end), and at the dimmer/fixture (receiving end) of a DMX link. Dimmers may have the ability to set a single DMX Start Address for the block of channels, or alternatively it may be possible to set a different DMX Address for each channel. Moving Lights generally have a single DMX Start Address for the fixture, although some (notably Vari*Lite units) will have a second DMX Address for the dimmer channel.
DMX Addresses were traditionally set using Binary Addressing with DIP Switches, although other user interface controls on the device are now more popular, especially on higher end fixtures. These other alternatives usually take the form of rotary switches (e.g. on older Chroma Q scrollers) or more commonly LCDs, which often give access to further options too on more advanced fixtures.
N.B. Some fixtures will require you to set the unit address rather than the DMX address. This means they can only be assigned start addresses of a certain multiple, consult the user manual for translations of unit address to DMX start address.