I think this is what you are asking:
In the Administration Console listing, double-click the PST name to display the PST properties.
Do one of the following:
Next to Mailbox, click Browse and then select the mailbox of the user who owns the PST file. The corresponding archive is automatically chosen.
Next to Destination archive, click Browse and then select the mailbox archive of the user who owns the PST file. The corresponding mailbox is automatically chosen.
Once you have completed the mailbox and archive details, the status immediately changes to Ready to copy.
That is an excerpt of the help from the admin console.