Hi Lara, yes just to clarify you don't need to install a script to create a basic helix, it's a built in tool which you can find under Draw curve > More > Helix.

If you want to run a script for a more specialized type of helix, there are instructions for how to install a plug-in in the FAQ here:
http://moi3d.com/faq#Q:_How_do_I_install_a_plug-in_script.3F

Thanks, - Michael