You can use paypal for renewal payments but you must renew several domain names at one time to use this method. This is because Moniker requires a minimum amount of $25 for all paypal payments and that amount is typically more than the cost of one domain name renewal.
To use paypal, use the pull down menu to renew the domain name(s) (this is described elsewhere) and wait about 30 minutes to an hour for Moniker to generate one or more invoices for the names.
To make a paypal payment, you must be able to view the one or more invoices under the "invoices" link so sometimes you have to wait up to an hour for them to appear.
Once you can view the one or more invoices for your domain name renewals, go to the "Payment Options" page on the left side menu bar and, once you arrive on the payment options page, click the paypal link (found in the middle of the page) and it will offer you a selection of invoices to pay.
Check the boxes to select the invoice(s) you want to pay and complete the paypal payment at paypal. You should then get a confirmation of a "paypal payment pending" and, typically within the hour, the domain names on the invoices should be renewed.