There are a multitude of resources online that could help you in learning automation testing. I personally went through a couple of blogs and videos online to learn automation testing and selenium from scratch. I found this particular playlist very helpful.
If you wish to learn automation testing in-depth and also get certified in it, you must check out Edureka's course for the same.
Do check it out https://www.edureka.co/selenium-certification-training
Hope this helps!