You can send out payment requests from within any of your membership packages.
Select the membership module and the membership package.
You can then filter for the members who are marked as 'Not Paid'.
Select the members record that you wish to send the request to, this will display the members details. You can then select 'Request Payment'.
The following overlay will appear where you have the option to add any additional text that you would like to appear in the email:
