You need to put this between grip and pommel, then put a kyber crystal inside. There's no led, so you need to buy crystal like this

https://www.etsy.com/ca/listing/715145524/star-wars-lightsaber-kyber-crystal-100?ga_order=most_relevant&ga_search_type=all&ga_view_type=gallery&ga_search_query=kyber+crystal&ref=sr_gallery-1-1&bes=1&organic_search_click=1

You also need to glue this crystal to chamber. (That's my very first work, so i don't know if it works well)