Enter Creative Mode or use commands
Collect 12 Eyes of Ender
Obtain 12 End Portal Frames
Build a 3-by-3 portal frame outline with a 1-block center opening
Place 3 frames on each side and 3 on each end
Make sure all frames face inward toward the center
Insert 1 Eye of Ender into each frame
Fill all 12 frame blocks with Eyes of Ender
Step into the activated End Portal to enter the End dimension