The key to finding the end portal is to find the stronghold and then navigate your way through it to the gateway hidden within. Place eyes of ender in each end portal frame to activate the portal.
The enderman can then be routed to a collection point where they can be farmed.
How to find enderman. Find the end portal frames under decoration blocks and place them in a 4 x 4 horizontal square leaving the corners and interior empty. An enderman will die in the rain. An enderman can spawn in areas with light level 7 or less 11 or less in the end on any solid surface having at least three empty spaces above.
Once an enderman has spawned in the dark it can survive in the daylight. I got 4 pearls from one enderman using looting iii. You can also find endermen in the nether now and you can even trade for pearls with villagers although i have not personally tried either route to see how much faster it could be.
This makes it teleport away and just completely rage and it could get the first hit. Find a flat area or a hill top that allows you to see a long way. Enderman spawn uncommonly on land and in caves in groups hauntings of up to two.
When you spot an enderman you jump off aggro and kill them then clamber back up. They spawn in all dimensions. Rinse and repeat and you should be done in a few hours.
Eyes of ender are your solution to the first problem there. Where to find an enderman. By naming the endermite and trapping it in a boat or minecart a permanent lure is created and all enderman that spawn within 30 blocks and sight of the endermite pathfind to the endermite and attack it.
It is very important to place portal frame blocks and ender eyes in the right direction. Get yourself a sword enchanted with looting. This is a wall enclosing a large well lit area that mobs can t spawn in.
They can spawn anywhere yes but they tend to only spawn in dark areas. In creative mode you can make your own end portal. The outside of the wall has an overhang to stop spiders climbing up.
You can also find enderman in the end biome in large numbers. In minecraft you can find endermen in most overworld biomes in light levels of 7 or less. That way you hopefully won t have to find 12 of them.
The best place to hunt endermen is in the desert because you can see them against the light sand at night. Build a hunting lodge. Do not however look in the eyes.
Also while i don t believe they are harmed by sunlight or spawn at day endermen aren t as restricted.