Rosa,
The door/window, modules are automatically assigned to the DS7000.
The first one you rigister will be #1 (first light on the console) the second one will be #2 etc.
up to #8. Then the ninth one will be #1 light again #10 will be #2 etc. This aids you in determining which door or window is open or have a problem such as low battery.
Remember that if you mess up while registering these modules (registering the same module twice for instance) the light on the console will constantly blink. The only way to correct this is to start over by unplugging the console and removing the battery for about 15 minitues.
The security remotes and motion sensor are also automatically registered.
For others such as switches, appliance modules and the like they have 2 code wheels one has numbers the other letters. To use them with the console the letter on them must be the same as the letter you set the console to. You can use any letter you like. (Most people avoid using the default factory code letter A.) Then use the number wheel to set them individually. For instance. Console letter C, you can then set up something like this. kitchen light C1, Coffee Pot appliance module C2, PowerHorn siren C3. You can then control them with remotes that are also set to the same letter.
There is a lot more information available here on the forum. You just have to do a search or two.