Hi, Suszua, welcome.
It's tricky to add a new plant-from-seed to an existing garden, because the baby won't get enough light. If you could maybe juryrig starting the plant under another light, or in a bottle, so it's closer to the lights, then transfer it into a hole when it's established-but-not-too-big-to-get-roots-into-hole, that might work. Cilantro is also a little tricky to germinate in the Aerogarden. (Basil is easy.)
Moderator. Author of Indoor Salad, Ecigs 102, and the Calm Act climate apocalyptic series.