click on 'Bitcoin' in the menu on the left hand side then look through the recent transactions list. they are in reverse date order so you might need to click on the 'load more transactions' button if the withdrawal was a few days ago
when you find your withdrawal it might say COMPLETED next to it, or PENDING
if it says COMPLETED then you can click on it and it will show you the blockchain transaction for the withdrawal
if it says PENDING then I dont know why it is taking so long - all mine have gone to COMPLETED within 24 hours