As a Seller, if you would like to offer the "Pay Later / by Check or Money Order" feature to your buyers, you can enable this from the Members Area > Store page:
Click the checkbox to enable the feature, and then click the blue submit button at the bottom of the page to save your changes.
Once enabled, buyers can request to become pre-approved, per the workflow shown above in the Pay Later for Buyers section. As a Seller, you will receive an email notification when a buyer requests to be pre-approved to Pay Later. You can also access the messages / requests from the Members Area > Messages section.
To approve a buyer, review their request, send them a quick response, and be sure to check off the "Approve Request" checkbox, and then click the blue submit button: