There’s only 1 artifact. A static executable. No “need” for a package manager. If someone builds a package manager they would just need to compile the src and ship the executable.

All you need to do otherwise is add it in PATH.

Download latest "nnd" file from https://github.com/al13n321/nnd/releases and place it somewhere you like.

Set the executable bit (using chmod or your file explorer's properties tab).

The program is now installed.

You can always build it yourself and put the binary somewhere in your runtime path.