I don't know what you've done so far so let me begin from scratch:

• Go to nem.io and download the most recent version of NEM software here: http://nem.io/install.html
• Istall it and everything is ok you should see the wallet (NCC) apear in your browser tab
• Create wallet - name of the wallet should not contain spaces or dots; also please choose a strong passwor (at least 12 characters)
• Once logged in your wallet you should see your address on the left side which you can use to accept XEM
• Please make sure you make a backup of your wallet files

http://support.ournem.com/knowledgebase.php?article=3

Then go over Poloniex and buy some XEM. When you have your XEM you need to send it to your address in your wallet.
To do that go to https://poloniex.com/balances and find your XEM balance. On the right from your balance there are fields where you can set the amount and the address (use your wallet address), you don't need to put any message (but you can if you want) when withdrawing the funds from Poloniex. Click on Withdraw XEM and your XEM should be visible very shortly in your wallet!

If you have more questions, and you probably have, feel more than welcome to join our official forum: https://forum.ournem.com/ or submit a ticket on support.ournem.com
We welcome you in NEM! :-)

If you want to buy a million or more there is an auction.

https://forum.ournem.com/nem-news-alerts/yes!-auction-2-is-live-now!!-3175/

But withdrawal from Poloniex is pretty easy really. Just go to the Balances page, fill in the amount to send, your account ID and the message generated by the system , click on Withdraw XEM.

http://i.imgur.com/1qVY1Me.png

Hi do you have an account at one of these exchanges?
https://poloniex.com/

https://bittrex.com/

https://bter.com/

and there are a few more