Once your offer is accepted or you have placed an order, Reverb asks that you submit payment within 72 hours. Orders that are not paid within 72 hours may be cancelled by Reverb. Buyers who repeatedly do not pay may be subject to negative feedback and account suspension.
Once paid, the seller is also required to supply a tracking number to the order within 72 hours, at which point you'll receive an email notification with a link to track your package.
If you have an unpaid order you need to submit payment for, just head to your orders page in the "Buying" section of your Reverb account, or click on your "Unpaid Orders" notification in the upper right hand corner of the site.