For stable versions, use this
haxelib install hscript-iris
For unstable versions however, use this
haxelib git hscript-iris https://github.com/crowplexus/hscript-iris/
Once this is done, go to your Project File, whether that be a build.hxml for Haxe Projects, or Project.xml for OpenFL and Flixel projects, and add hscript-iris to your libraries
--library hscript-iris
# this is optional and can be added if wanted
# provides descriptive traces and better error handling at runtime
-D hscriptPos<haxelib name="hscript-iris"/>
<haxedef name="hscriptPos"/>