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.