You can make an End Portal in "Minecraft" by adding twelve Eyes of Ender to a broken portal. In Survival mode, broken End Portals can be found in underground strongholds scattered across the world ...

Once you find the End Portal room, you’ll need to fill up the portal border with 12 Eye of Enders to activate it. (Some of the slots may already have Eyes, which means you’ll need slightly fewer.) ...

How to make an End Portal in Minecraft. Unless you're playing in Creative Mode (where you have access to every block in the game), there isn't any way to build an End Portal from scratch.