How to export members addresses into spreadsheet for a mailout?
You can use find contact search or Advance search or find membership search. Perform search and then select the contact you want to export and from task drop down select export, and select 'Export PRIMARY fields' or 'Select fields for export' if you don't want all fields.

Ref: https://docs.civicrm.org/user/en/4.6/common-workflows/exporting-your-contacts/