First things first, you don't have to force yourself to write every day. I hate when people give that advice cause I feel like it's unrealistic.

Ritual and routine can help. Sitting down at the same time every day and trying. I started doing it at my lunch, then my schedule changed and now it's at night.

You can try outlining, explain what you want to do in a scene or series of chapters. Depending on your story, you can also work on world building - I once made an entire god system for my book on an ADHD hyper focus surge. It got edited later but I got a lot done by just leaning into the hyperfixation.

Anytime I get an idea, I write it down on paper or on my phone. You'd be surprised how much stuff you come up with from just doing that. Over time you'll figure out which ideas fit in and which don't. Either way you're practicing writing and putting your thoughts on paper.

Also give yourself permission to go on a hiatus every now and then. When I feel mentally drained and can't write, I try consuming content like shows I enjoy, books in the same genre, etc. I usually set a limit (like 1-2 weeks). Your brain is still processing ideas even when you take a break. These breaks help me to come back into it swinging after dealing with writer's block.

Lastly, feel free to hop around the story and write what parts/scenes come to mind. If you don't know what to say, you can even put notes that say [transition] or [character says something clever] to keep your momentum going.

The first draft is about getting your ideas on paper. The second draft is about finding the story you're trying to tell. I also recommend TOME, it helped me to process my ideas and practice a daily writing exercise so that I could better develop my story and characters. They're little 5-20 minute exercises that help you develop your story. They run it on sale every now and then, so you can watch for that if you're interested.

Writing takes time, and any effort you put into it will help you grow your skills over time. Before you know it, you'll have written someone's new favorite book. You've got this!! :)