how to make mailing labels on pages

If you are using Pages, then the hard way, as it does not feature Mail or Data merge capability. Although in the U.S., Avery does offer blank mailing label templates in Pages document format, you still get to painstakingly fill out one label, and duplicate across the entire sheet, or if different addresses, you can spend hours at this.

Apple's Contact application will allow you to import a text CSV of names/addresses into a custom contact group. With all of the names in that contact group selected, you can then visit the print menu where you can select the Style as Mailing Labels, and then the Page as your particular Avery mailing label product number. If it is a sheet of mailing labels with the same content, you would need a custom group with that specific contact duplicated as many times as there are labels on the sheet, select those, and then print.

See Contact Users Guide.