1. Open Outlook and select "File" top left



2. Select "Info" on left hand side then select the "Account Settings" tab and "Account Settings...."



3. Select your email account and click "Change..."



4. This page should appear click "More Settings..."



5. Select the "Advanced" Tab and click "Add..." then type in your additional mailbox name you wish to add and click "OK"



6. It will auto complete double check name is correct below and click "Apply" then "OK"



7. Back to this screen click "Next >"



8. Click "Close"



9. This should bring you back to your Inbox the additional mailbox should now be displayed below.



Note: this will not work unless we have given you access to the specific mailbox you are trying to add.
 
this is also only for view access not send as.