How do I import my Outlook 2013 PST file into Office 365 and then have them permanently synced?

I have Office 365. I have Outlook 2013 downloaded on my computer with all my emails and contacts, etc.

I want to import the entire PST file with my emails, contacts etc. into Office 365 / Exchange Online (cloud?). Once that is done, I want to set it up so that my Desktop Outlook will always update and sync with my Office 365 when I am out of the office and use the Outlook mail App.

PLEASE HELP!