Hi Kovan,
You can buy more numbers by going to the "Numbers" tab in your top menu and selecting "Numbers." On the next page, you'll see a button (on the left) that says "Buy Phone Number"
You might find this page from our resources section helpful, as it explains more about buying phone numbers:
https://www.ringroost.com/how-to-buy-phone-numbers.php
This help video walks you through the steps of buying a phone number (about 5 minutes in):
https://www.ringroost.com/help-videos.php
I hope this helps. Let us know if you have any more questions.
Thanks,
RingRoost Support Team