In order to set your vantage point, you'll need to specify a latitude and longitude. You can look them up here using the code for a nearby airport. You don't need to be very precise; any major airport within 100 miles or so will be fine.

Step 1: Enter the code for your nearest airport (e.g. LAX).
Step 2: Find your coordinates.
Step 3: Send your coordinates back to the "Create an Image" page.

Some other good sites to look up your latitude and longitude are:

The airport locator database was originally obtained from An updated version is here.