JASS into WE

How do I transfer a JASS script into my WE triggers?

You must first convert your trigger to a custom text window; there is an option to do so in one of the trigger editor menus.

he wants JASS > GUI conversion...

If you want to copy a Jass script into your map, create a new trigger, select it, use Edit -> Convert to Custom Text and replace all the text showing up in the trigger with the desired script.

If you want to convert a Jass script into a Gui trigger... well, thats simply not possible.