Get you a large large box or tub. Cover bottom with newspaper. Hang the light bulb down towards one end about a foot away (make sure it doesn't touch the box so no fire threat). Put a small dish of water about a foot or 2 away and the egg yolk on a small dish there too. That way when she's cold, she move close to the light bulb. If it's too close to her, she'll move away. Take your cues from her .. huddled under the light bulb means she's still too cold. Far away from the light bulb means you could move it up more. But she'll move away to get the food and water, getting exercise.
I really advise you to get a heat light bulb. Those are red. They provide heat, but not necessarily the light. They need the "daylight" off during the night to help establish sleep patterns, and give her some "off" time although for the first several weeks, they'll still eat and drink and play at night. So a regular light bulb really isn't the best thing.
Seriously, you should get to a feed store today. Get the red heat light bulb and the special lamp it plugs in to. Get the chick starter feed (medicated is fine), and chick feeder and waterer. These will help your little buddy get through these first few days.
Also, they shouldn't be left alone, so either get another chick or two, or pass her off to someone who has chicks. They get lonely.
Good luck.