This is a good thing to read when you're starting out.

https://lospec.com/pixel-art-where-to-start/

After that, you might be wanting to animate the sprites. That's new set of skills, and you'll need to practice all the different kinds of animations, like walking/running, attacking, jumping, getting hurt... etc.

4 hours ago, CrossAlex21 said:

I am an indie game dev and currently, I don't know where to start drawing pixel art style. I've already made the code but I don't know the design. Can somebody give me a tip for starting to make Pixel art?

I had the same requirement, bought a course on Udemy. Never got around to watching more than ~1 hour so can't say if it works.
If you're a video-learner take a look at offers on Udemy perhaps. There were quite a few high ranked ones.

Good luck!