ive downloaded hearthfire and it shows up when i look at my storage but the courier never gives me the letters and i talk to the stewards and the option to purchase land is not available.

Have you already bought any houses like whiterun, markarth etc?

If you have you should speak to the stewards about buying decorations. You should now have and option to buy a children's bedroom if hearthfire is installed properly.
You will get the option to buy child's bedroom even if couriers haven't delivered to you.

b ut what about purchasing the land? and i have all of the houses except the ones in the hearth fire DLC.

You will be able to buy the land off the jarls stewards in morthal, falkreath or dawnstar.

Before the options become available you need to have done certain quest for the jarl. In morthal you need to have solved that vampire quest.
No courier deliveries are required

Easiest thing:

1. Go to an unrelated cell (i.e. not Morthal, Dawnstar or Falkreath. Save and exit.
2. Delete the DLC - it'll be under something like System Settings, My Games or suchlike.
3. Load the game, ignore the error message, save and exit.
4. Re-download the DLC.

Now when you go back into the game, you'll get both letters and be able to buy the land.

(NB you do need to be "in good standing" with the Jarl, i.e. done one of his/her quests or be the Thane.)

ok. next time i get on skyrim i will try and see if this will work. thanks.