If you would like to go from the very beginning (no or minimal programming experience): https://narimiran.github.io/nim-basics/ (disclamer: I'm the author of that tutorial)
If you are more experienced, and you want to explore all the possibilities that Nim provides, check the language manual: https://nim-lang.org/docs/manual.html
If you need any help with getting started, join Nim channel on IRC/Gitter and ask the questions. The community is very friendly and helpful! (It is one of the main reasons I kept using Nim in my Nim beginnings)
I understand that it might suck to be buying a book to learn a language, so just in case you don't want to commit to that there are two chapters of the book which are free. You can find them listed in the link above or here: https://book.picheta.me/
And the notes:
was always my favorite "how I start". I see it was updated in February - I'm not sure if it's aged well / bitrotted.
But looks like there might be commenters close by that do know?