Hi, Molly, and welcome to NGA. Asking questions is how we learn and you are asking the right ones.
You are very lucky this cutting rooted. They are very finicky plants to root and I don't even bother to try to root their cuttings. I air-layer my "Mother" plant, and that's way more predictable.
I would go ahead and pot it up, perhaps starting in a 4" pot. Use regular (commercial) potting soil but for every quart of soil, add a small handful of coarse perlite. You want that soil to be well-draining. Put the potted plant in bright light, but no direct sunlight between the hours of 10:00 AM and 4:00 PM. Fiddles can be adapted to full sun, but if this is going to be a houseplant, you only want to give it early morning or very late afternoon sun.
As much as possible, keep that potting soil constantly moist. Not sopping wet, mind you. Because of these large leaves and quick growth, you may need to water every day. It just depends on the heat, light, and air-movement. If the soil dries out a bit between waterings, the plant will still do fine. It will simply grow more quickly and be healthier with constant moisture. This is a tropical tree. In 6-8 weeks, move that plant into a 1 gal. pot, using the same potting soil/perlite ratio.
