Click File Tab ,then Open , then Import
Choose Export to a file, Click Next
Choose Outlook Data File (.pst), click Next.
Browse and select the Folder to export, Tick/Untick Include subfolders, click Next.
Browse where to save file to, give approriate name, choose what to do with duplicates, click Finish.
Add a password if required
You will see a similar dialog to below to show the export status.