a. Start Outlook email client and locate PST files to be merged
b. In order to create new Outlook PST file, you have to click on New Items > More Items > Outlook Data File
c. Create or Open Outlook Data File window will pop up. Define a name to this new PST file and click OK
d. You can find the new PST file in the navigation tab. Now you have to Click File tab, then select Open and go for Import option
e. As the Import and Export wizard will be opened you have to Choose “Import from another Program or File” option from the list and then click Next
f. Now Select file type (.pst) to import from and then click Next
g. After this Browse to choose the file and check the box “Do not import duplicates” and click on Next
h. Finally choose the folder to import and you have to check “Include subfolders” and “Import items into the same folder in” check boxes, and then click Finish.