X10 wiki has the following: (This is how I program Socket Rockets)
If you purchased an ActiveHome Pro kit without a remote, you can still program your LM15A by initially defining it as a Chime Module. You will also need a small lamp.
1.Expand the Modules category in the Group Pane (left side of the screen) and click on the Other subcategory. Drag the SC546A Remote Chime (it receives only an On command, necessary to LM15A programming) to the top half of the screen. Select the House and Unit code you want your LM15A at, and hit OK.
2.Without the Socket Rocket installed, confirm that the lamp is turned on; then unplug it from the wall without turning it off.
3.Remove the bulb, screw in the Socket Rocket, and screw the bulb back in.
4.Plug the lamp into the closest outlet to the ActiveHome Pro Computer Interface-ideally, one in the same outlet pair. Immediately start clicking repeatedly on the Remote Chime icon. Continue clicking until the lamp comes on or thirty seconds have passed.
5.Right-click on the Remote Chime and select Edit Module. Change the Type of Module to Lamps, then change Module to Socket Rocket and click OK.