Here is some previous discussion:
Show HN: Getada: rustup-like installer for Ada's toolchain/package manager 194 points | 115 comments: https://news.ycombinator.com/item?id=40132373
There is a quickstart with a link to a large tutorial: https://www.getada.dev/how-to-use-alire.html
If you wanna try out Ada without even installing anything, you can also check out https://learn.adacore.com/