I used this as a reference when I started working with Miniscript a few years ago: https://bitcoin.sipa.be/miniscript/. It's very detailed and I'm not quite sure how up-to-date it is, but the section titled "Policy to Miniscript compiler" is interactive and can help you understand how to use it.

One thing that is important to keep in mind is that Miniscript sits in between two other languages: the low level Bitcoin Script, which is quirky and hard to use, and the Miniscript policy language, which is high level and more user friendly. As a writer of Bitcoin contracts you almost always want to work with the policy language. Some have even written languages on top of the Miniscript policy language e.g. Minsc.

Anyway, I think Miniscript is amazing. It made working with Bitcoin Script so much easier for me.