Go to 'wallet' tab, on the 'balance' screen you'll see all your balances including bitcoin (crypto balance column).
Next to Bitcoin you have 2 options, deposit and withdrawal. Click on withdrawal and you'll see a screen where you can enter address ("Enter the recipient's address below"). Paste your address there, enter the amount on the right and click withdraw.
Next time buy on exchanges
, better rate. I remember cex.io from shady mining contracts and taking over 40% of whole mining power year ago around.
It was ghash.io and they had over 50% of total mining power for a short while. But that's in the past.