Embarking is answered in this video the project put out. looks like a combination of 'drone pods' that land on the helicopter pads on the back legs. ( the pads seem to be partly tucked under the overhang of the upper stage? that doesn't seem safe for anybody ) and a tunnel through the side that enters the docking area in the center of the ship that looks like it would be fun to pilot through. https://www.youtube.com/watch?v=XT_3YmlXvOI