Start with an Attendee List Export located at Event > Event Data > Exports
Once this export is complete, edit it and delete columns until you have 20 or less. We suggest keeping First Name, Last Name, Title, and Organisation, but your needs will be unique.
Save this export and go to the Avery Print & Design site.
These two helpful Avery tutorials cover the quick start usage of the site (2:54) and then the process of importing the file we created previously (6:53)
Attendease Support is able to provide limited assistance with the Avery site as we're not experts with its use but, as always, if you have questions don't hesitate to ask.