If you are very very new and noob at this I suggest checking the beginner stuffHERE. I will try to keep it simple with what you should do and when you should do it! Real simple and it's easy but very fundamental stuff you cannot get to a higher level if you don't master
Get a photo of your choice and click on Develop at the top of the screen which opens up the photo and tools to edit it.
Adjusting brightness of a photo, try clicking Auto in the Basic panel.
Use the Basic panel sliders to fine-tune an adjustment. For example, drag the Exposure slider to brigten or darken the entire image. That fixes theoverexposure (too much light).
To bring detail and texture there is Clarity slider, bring it to right. To soften an image, drag the slider to the left. Very useful for portraits
If a photo looks dull, drag the Contrast slider slightly to the right to increase difference between light and dark areas.
To make image more colorful, drag the Vibrance slider to the right. You can also play with different colors that way.
Experiment with the Temp slider to change the overall color to a warmer or a cooler shade.
To undo whatever setting you may applied Control+Z(windows) and Command+Z(macos). To remove every adjustment you made press the Reset button at the bottom right.
There's a history panel. There you can see every adjustment you've made to the current photo.