How do you slay the Ender dragon in mine raft or?

Here's a helpful tip from Primagames.
Before kicking off the boss fight, bring a Bow with the greatest Power enchantment you can find; have lots of Arrows on hand as well. On top of that, you need a sword with a Fire Aspect or high damage. Reason being, you’ll need it to slay the Endermen lurking about; the sword is useless against The Ender Dragon.

In regard to armor, equip Diamond Armor with Protection IV. A Pumpkin or Diamond Helm is good, but we think Diamond is the best way to go since it will keep you alive longer, whereas Pumpkin comes in handy for avoiding Endermen; look at these enemies while wearing a Pumpkin Helm and they won’t attack. If you don’t equip Pumpkin and look at Endermen, they come after you.

You’ll probably need to heal at least once during the battle, so have Potions of Healing and Regeneration, along with some Golden Apples or Enchanted Golden Apples. Finally, Ender Pearls allow you to teleport from a smaller island to the main island if you somehow get knocked off the edge.

When the boss fight against The Ender Dragon begins, make a point to destroy the End Crystals on top of the Obsidian Pillars. These crystals keep the creature close to max health, so it’s in your best interest to take them down.

The best way to destroy End Crystals is to look for healing beams, then follow them back to the crystals. Pull out your Bow and shoot them with arrows until they blow up.

With the End Crystals destroyed, go after The Ender Dragon with your Bow. Aim for it's head for quadruple damage. To achieve headshots, wait for the boss to chase you, then squeeze off a fully charged arrow, then another as fast as you can. The Ender Dragon will flee and you want to go after it (yes, chase the monster) until it goes on the attack again. When this happens, do the exact same thing as before. Repeat until the creature falls.

Gather experience from The Ender Dragon, along with the Dragon Egg. Click the egg and it teleports away from the End Portal. Do not allow the egg to tumble into this portal and break. You will need to search for the egg; look underground.