The way that you interact with a Shared Account is basically the same as any account that you own. You can add/manage records such as tags, contacts, and deals using the exact same methods that you would normally use on your own accounts.
Impersonating a User on an Account
When you impersonate a user, you are acting on behalf of them. Everything that you do with the account will be associated with them. For example, if you add a deal while impersonating the account as someone, then that person will be the owner of that deal. Impersonating a user also allows you to see just the information associated with them. For example, if you view the Deals tab, you will only see the deals that person owns.
To choose a user to impersonate, select a name from the Viewing Account for field (located in top left corner of Account profile page). The field also contains an All option which will allow you to see a combined set of records. For example, if you view the Contacts tab while viewing the page as All, you will see all of the contacts associated with the account, regardless of the owner(s). If you wish to add a contact or activity to a shared account and need to be the owner of that record, make sure that the field is set to All.
Note that when the field is set to All, you cannot perform certain updates such as updating the address or managing tags.
In summary: If you are viewing the account as another user and add a record, then that user owns that record. If you are viewing the account as All and add a record, you are the owner of that record.
Keyword Search: Shared Accounts