regarding symbol: If the connector has 80 pins overall then you can use the Conn_02x40 … (choose the pin numbering style that suits your needs) symbol as found in the official lib. If it has 160 pins then you will need to make a symbol for yourself. (Either extend the script to generate one for you or make one by hand or find another generator. https://github.com/KiCad/kicad-library-utils/tree/master/schlib/autogen/connector)
Rene already gave a link for that above. There’s nothing special in an edge connector, you just have to place it carefully in the layout. At the moment KiCad doesn’t support edge line in footprints, so you must draw the Edge.Cuts outline in the board and add the footprint to its place.