For me Enchanting has always been the 2nd most complex thing in minecraft (The first being potions) so hopefully this will help you

First things first we will need a Enchanting Table which can be crafted like this

B= book D= diamond O= obsidian B
DOD
OOO

To work it we will need EXP You gain that by killing monsters

Once you have a couple of levels (atleast 5) go and place your table down be sure to place it in a place with lots of bookshelves to power it up

then put any tool weapon or armour in the square

Now all you see is a load of mombo jumbo so your getting any old thing

You see the green number thats the level you need to get the Enchantment

Just click the bar to get your Echantment

Hope this helped if it did give me a diamond :)