Where can I learn to get better at eating pussy?

I did it for the first time for my girl since she's been asking me to do it a lot lately and she gave light moans but it didn't do shit for her. When I give her dick she screams and shakes.

I basically flicked my tongue back and forth on the hood of her clit because I can't even find her actual clit.

I honestly felt ashamed of myself for being so bad at it.