Here are the instructions to backup Outlook 2013 or Outlook 2016 to a PST file.
1. Click on File
2. Choose Open & Export > Import / Export
3. Choose Export to a file
4. Click Outlook Data File (.pst) and then click Next
5. Select the name of the email account to export. Only one account can be exported at a a time. Make sure that Include Subfolders is selected, this will make sure all information will be exported and backed up
6. Click Browse to select where to save the file. Type a file name and click on OK to continue.
7. Click Finish to continue. If prompted for a password you can leave this blank as it’s not required.