Go to the 'store' tab at the top of your page, like Hazard said. Click 'buy credits'. You will need 1000 credits to buy VIP. Once you've purchased the credits you will need to click the 'store tab again, but go to the 'spend credits' menu instead. Underneath 'VIP' you will see two options: 'Purchase for yourself' 'Purchase for a friend'. Click purchase for yourself and then click purchase again when you're on the next page.
After you've done all that you should get it instantly as far as I am aware.
Hope this helps and happy VIP'ing to you