The first time you start Geary, you will be prompted to add an email account. On this screen, select if your account is Gmail, Yahoo, Outlook.com, or other. For other account types, you will need to enter your IMAP and SMTP login settings manually.
Additional accounts can be added from the Accounts dialog. The Accounts option is available in either Geary's application menu or the gear menu in the upper-right of the toolbar. (The location depends on the install desktop shell. For GNOME Shell and Unity, the application menu is available near the top-left corner of the screen.) Alternately, Ctrl+M will open the Accounts dialog. To add an account, click the + button.
From the Accounts dialog, select an account and click the pencil icon to change various settings. Please note that Geary cannot change server settings on an existing account. If you need to change your IMAP or SMTP server, you will need to delete the account and re-add it.
To change the order that accounts are displayed in the folder list, drag the accounts in the Accounts dialog to the desired order.
There are some advanced options available when editing accounts:
The Save sent mail checkbox controls whether Geary will push successfully sent messages up to the account's Sent Mail folder. For Gmail accounts, this happens automatically. Yahoo and some other accounts can be configured to do this automatically as well. For other accounts, if you disable this setting, you may be unable to view messages you've sent.
The Download mail drop-down allows you to configure how much mail Geary will keep locally. Geary can only use locally available mail when searching and forming conversations.
To delete an account, open the Accounts dialog, select the account, and press the - button. Geary will delete all information associated with the account.