Note: Load up the tutorial world and head to the section with animals, grab the wheat there and go to the cows and make them mate, read the rest of the solution if you're confused with the rest
To get this achievement, you must breed two cows with wheat.
This is fairly simple, first off, you need to obtain wheat, these can be obtained by luck in dungeons, but there's an easier way
Spawn into a world and you should see Grass sticking out the grass blocks, hit these until Seeds come out. Two is required, next, craft a wooden hoe, and fertilise some of the land, make sure it's right beside some water.
Next, plant the seeds and wait. If you can't be bothered waiting, when it is night time, kill some skeletons and collect their bones, craft bonemeal and use it to instantly grow the crop, harvest the crop.
Next up, hold the wheat in your hand, this will make animals follow you, as they want to eat it. We are only looking for two cows.
When you have two cows following you, feed one of them by aiming your cursor at them and pressing
, do the same for the other one, they will do some sort of kissing things and then out will come a baby cow. Achievement Unlocked.