There are some excellent answers listed below or above with different lists of tools and technologies you can learn.
However, if you are an absolute beginner, that can be overwhelming and you find yourself doing multiple tutorials at the same time and not really making any progress.
So I would recommend starting with a concrete task: automate some scenarios for a test page. You start with a goal in mind and you expand your knowledge when you notice a need for it. That way you are learning only that that you will use and you will see an immediate result. Seeing the result is very important for the feedback loop for your learning.
Here is an example task:
You might start with Selenium, for example. So you will start solving a problem at a time: install Selenium, search the internet, set up Selenium, some more googling, browse this page. Then you notice you need to understand more Java (if that is the language of choice), so you will take a tutorial for begginners and so on.