Before you begin, you will need a shapefile (a set of four files with the extensions: .shp, .dbf, ,shx, and .prj) that contains the data that you want to map. TileMill supports a number of the most commonly used geospatial formats, you can read more about the types of supported layers here.
There are a number of resources to obtain shapefile data for the area or issue you want to map. You may also have generated your own data in shapefile format and want to map it alongside other data.
If you need to do additional manipulation or edit your shapefile, you can use free open-source software like QuantumGIS to work with shapefiles. LibreOffice (or OpenOffice) are also free and allow you to edit the
.dbf file, or the file with attribute data.
#countriesstyled with some example CartoCSS code.
platesin the ID field. You’ll use this ID to reference this layer in CartoCSS selectors.
trench.shpshapefile located on your computer. You can browse your folders to find the source of your shapefile.