After downloading the application, install it. Here the view when there are no downloaded accounts:
Click on the button ADD and sign in with your Google Account. Download the accounts and now you are able to do changes offline, and then upload the changes to AdWords.
AdWords Editor can help you save time and make it easier to make changes in bulk.
What is possible to do on Adwords Editor: Use bulk editing tools to make multiple changes quickly; Export and import files to share proposals or make changes to an account; View statistics for all campaigns or a subset of campaigns; Manage, edit, and view multiple accounts at the same time; Search and replace text across ad groups or campaigns; Copy or move items between ad groups and campaigns; Undo and redo multiple changes while editing; Make changes in draft before uploading; Keep working when you’re offline.