Within Entourage, there are 2 mailboxes. The first is your Samuel Merritt University account mailbox and the second is a local mailbox 'On My Computer'
Under 'On My Computer', highlight the Inbox and Option+click (right-click) and choose New Subfolder to create a folder under Inbox. Label this folder according to what you are going to copy from your Samuelmerritt mailbox
Now go back to your Samuel Merritt email and grab the messages you want to archive. (Hint: you can highlight the first message and hold down the SHIFT key and click on the lsst message to highlight all the messages in the folder)
Option + Click (right click) and choose 'Move To' (choose folder)
Choose the subfolder you just created from the list
For folders like 'Sent Items, Deleted Items, and the 'Inbox' folder, since these folders are already present under the 'On My Computer' mailbox, you can skip the subfolder creation step and just copy the messages.
Once you've successfully copied the messages you want to archive, you'll need to delete them from your Samuel Merritt mailbox.
To delete, highlight the messages, Option + click (right-click) and choose 'Delete Message'