3 Glass
5 Obsidian
1 Nether Star
Open a crafting table
Place the 3 Glass in the top row
Place the 5 Obsidian in a pyramid shape with 3 in the bottom row, 1 in the middle of the second row, and 1 in the center of the third row
Place the Nether Star in the center slot
Take the Beacon from the result slot