In this example I have a photograph where I'd like the eye to focus on the entrance of the building. It's a little dark so I want to brighten up just this area.
You'll find the Radial filter in the toolbar at the top of the screen. You'll also see numerous settings on the right side of the screen.
What's nice about the Radial filter is that you can edit just an area (or several areas) of the photograph without changing the rest of the photo.
You can drag and draw an area as desired. Don't worry if it's not perfect. You can easily drag and move the selected area and even resize the shape by dragging on the handles around the edges of the oval.
Once you have the area selected you can start using the editing tools on the right side of the screen.
In this case I changed the feathering to soften the effect. I bumped up the Exposure setting to brighten this area. You can change numerous things like the contrast, color and saturation by just playing with the sliders available in the panel.
When you get the effects you want, just click the OK button.
Camera raw gives you the tools needed to fix and adjust your photographs exactly as needed.
Want to see more about these tools?
Take a look at using Camera Raw Brush.