If your chip count is lower or equal to the 'Maximum chips for rebuy' amount, you have the option to rebuy.
Click 'Rebuy'. The rebuy window will then appear and you'll have 60 seconds to confirm the rebuy.
Your rebuy amount will be transferred from your 'Available Money' to your 'Money on the Tables'. A message will appear to inform you that the request is being processed.
A confirmation message will also appear once your request is approved.