Get out and look around
The best way to get started is to take photos of your home and start sketching out where you want to add lights. There are a ton of props out there, so you may want to skip ahead and look at the PROPS info page to get a better idea of what your options are.
When you take a picture, you can either print it out or use an application on the computer and start laying shapes of the props on the house. once you have a general idea of what you want, you can start ordering the props or start building your own.
Below are some examples.
Syracuse Lights (in Syracuse, UT, USA)
Lights on Justice (in Fort Mitchell, AL, USA)
Lindsey Lights On Yorkshire (in South Jordan, UT, USA)
Lights on Fitzpatrick (in Kelowna, BC, Canada)
When you get more advanced, you use a tool like hover.to to get your house into a 3D model, then import it into xlights to set your lights into motion in 3D.