Fnf Setup error

This has been fixed, but I am running a test in the Psych Engine: lime test windows. It gave me back the error “Error: Could not find haxelib “flixel” version “5.6.1”. Does it need to be installed?” How do I fix this?

btw, I am using www.youtube.com/watch?v=4IuC8ti6_4o as a tutorial