DISCLAIMER: This is an unofficial application for Minecraft Pocket Edition. This application is not associated in any way with Mojang AB. Minecraft Name, Minecraft Mark and Minecraft Assets are all property of Mojang AB or their respectful owner. All rights reserved. In accordance with http://account.mojang.com/documents/brand_guidelines

You must find a Kyber Crystal, which can be found on another planet (the Nether) that is heavily guarded by Stormtroopers. They can also be found in the creative inventory. Then once you obtain a Kyber Crystal, you must place down the Hilt Table, and use your crystal on the table. You will also have to then use an Iron Block on the table to create the hilts. Then you can cycle through the hilt choices and hit the table when you find the one that you like. Your Lightsaber will then be complete.