Olives aren't emulated hardware - they are actual Junos routing-engines (supervisors in Cisco terminology), so it isn't possible to add "WICs" as you would to a Cisco (which is being emulated along with the WICs) in GNS3.
You could possibly add extra Ethernet ports using the `NM-1FE-TX` option in the other Slot drop-downs but from memory when I built some physical Olives many moons ago I think this was limited to a max of 4 interfaces on top of the first `fxp0` port.