How to change settings in photoshop?

the setting in my photoshop change... and i don't know how to change it back. now i can't do some shadowing.How to change settings in photoshop?
To get all your settings back to the default you can delete your preferences file.



How to reset Photoshop preferences (In Windows):



1. First, hold down all three Ctrl+Alt+Shift buttons

2. Now ';while keeping those button held,'; simply open Photoshop

3. As Photoshop loads, you should get a prompt asking if you would like to ';delete the Photoshop settings file';, Click yes



You should now have a fresh slate with all of the settings returned to their default.



Note: I have found that this process is kind of fussy and doesn't always work and just opens Photoshop normally, so just keep trying until it does.