I had to bring a Green Dragonette home from the LFS, couldn't help it. I placed it in a 10g for a week to relax, then stuck him in a hang-on breeder box with a small heater and thermometer. I tried not to stress it out, and drank my coffee next to it in the mornings. Other times of the day I'd go an hang out near it but not futz with it at all. I feed my other clowns P.E. Mysis and had brine around from when they were smaller. After 4-5 days in the "box",, I dropped a few brine in and it started eating them. Now it's in my display tank and eats the P.E. mysis, Fauna Marin soft clownfish food, APBreed TDO chroma boost (sm). Pretty much anything I drop in. It may have helped that I had a Scooter Blenny in there to show it how to eat everything and anything. Oh yeah the blennys will do flake food also.
Mainly it gets P.E. Mysis treated with selcon, just like my Clowns.
Get the Dragonette, pick a big healthy one, feed it frozen food. Get a Scooter Blenny to teach it to eat if you need, things are eaters.
It just learned how to glide along the glass on the water currents in my ZeroEdge 22ZR tank.