Log into your emails and right click “Folder” on the left-hand side, when this menu appears select “Add shared folder”.
The following box should appear, type in the email address of the account you are trying to add and select it.
Once the email address is selected you should be able to click the add button.
Once you have added the account you will see it on the left-hand side, you can click the arrow and drop it down to view the emails as if you are logged into that account.
To send from an alternative email you can start writing a new email and select the box that says “from”.
This will show a drop down menu of all of the emails you are able to send from.
Select the email address you want to send from and then write and send the email as you normally would.