You need to create two footprints to represent an edge connector and you will also need two symbols. Using the footprint editor found by selecting Design > New Footprint layout the pads for the top side of the edge card. Save the footprint.
If you want to represent this on the schematic you will need to do some more work. After creating the footprints you can switch over to the schematic and create the symbols and pair them with the footprints created earlier.The parts creation thread will help you get through this process.
One you have the parts in your taxonomy you can place two of the parts on your schematic. The go to the layout to move the footprints into position at the board edge. Move the top footprint into position. Now place your mouse of the second footprint and press the o key to move it to the bottom side of the board. Move the bottom pads into position.