To export a folder(s) from Outlook 2010 do this:
Step 1: Open Outlook 2010 and go to File -> Open -> Import
Step 2: Choose ‘Export to a file’
Step 3: Choose ‘Outlook Data File (.pst)
Step 4: You will now get the see the folder structure of your mailbox, choose which folders you want to export and if needed select ‘Include subfolders’
Step 5: Give a location where the export saves the .pst file. And select, ‘Replace duplicates with items exported’. Make sure you give the .pst a new name. Click Finish.
Step 6: If you want, you can give the .pst file a password.
The export is now running, you can’t use Outlook while it’s running.