Start by using your trusted tool.

Use Adobe Photoshop or Adobe Illustrator to create the two necessary files: a color file and an elevation file. Adobe Photoshop can be used to create the files manually. For Adobe Illustrator you can get a little help of the Elevation Assistant plug-in that is currently free available for Adobe Illustrator versions CS6 and CC.

Do you want a little help or do you just want to make designing easier?

Get the plug-in here!