It really depends what you want to do! If you’re learning CSS, I assume you’re interested in learning how to build a website, so for that you can try out Learn HTML to learn how to build a webpage.
This is all covered in the Front End Engineer Career Path which can take you from zero experience to building a functioning website ready for deployment, as opposed to taking individual lessons.
The choice is really up to you what direction you would like to go in, but those would be my recommendations if you have learned CSS.
My recommendation would be learning how to set up VS Code, as you can then work on programs in your own environment and have multiple files open at once to make the development process easier. There’s some information on setting that up on the Codecademy website. You can also use a website like code pen if you just want a quick environment to practise in, there’s many options!