To capture a payment, click on the center number by the user in user management to open the payment tab in the user's side panel. Click the 4 dots to the right of the transaction --> capture Payment Now --> click Yes to confirm. 
An authorized payment is a payment that has been made by the user but has not yet been processed by the payment processor. The payment remains in an authorized state for 24hrs, during which time it can be canceled or captured. If you capture an authorized payment, the user will be charged.