First you need the actual portal itself.
Do this command:
/give
Note that the End portal looks like 2d wool in your inventory
Then place the End portal's in a 3x3 square.
If your in creative mode find the End portal frame and put it all around the End portal, including the corners if you want.
If your in survival mode do this command:
/give
Then you put it around the End portal.
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There is no way to build an end portal except on creative mode, instead you must find a stronghold which contains a portal using eyes of ender. The portal must be activated with 12 eyes of ender before you can travel to the end.
If you have the aether mod installed, you sure can.
You can create an Ender Portal using Ender Portal Frame blocks from your inventory and activate it using Eyes of Ender
4J Studios hasn't put in The End yet but there's still portal frames (creative mode only)
Download the mode or change the play mode to creative.