If your theme is compatible with BuddyPress and Grimlock for BuddyPress, two built-in menu locations are provided to allow you to display different menus for account related actions and links whether users are connected or not.
However, if you wish to show different primary menus for logged in or logged out users, you can use the Nav Menu Roles WordPress plugin (or If Menu) to easily show and hide different menu items depending on a user’s authentication or role. For more information please visit the Nav Menu Roles plugin page on the WordPress.org plugin repository.