You need to establish a network connection using PPP protocol. After that, just SSH using the IP address that was assigned while establishing a PPP connection.

Here are some links describing the process in more details, mostly on Raspberry Pi side:

• http://www.instructables.com/id/Connect-the-Raspberry-Pi-to-network-using-UART/?ALLSTEPS
• http://stackoverflow.com/questions/7011384/ppp-server-on-windows/7085259#7085259

Here is how to configure PPP connection at your Windows PC:

• https://mikebeach.org/2012/08/30/installing-and-configuring-a-ppp-null-modem-connection-on-windows-7/
• http://serverfault.com/questions/145259/powershell-win32-networkadapterconfiguration-not-seeing-ppp-adapter

How to create a Windows script to automatically add PPP connection and connect it right away with one click - for that, you might need to create a PowerShell script or CMD script using the info from the following links:

• http://www.digitalcitizen.life/how-automatically-dial-broadband-pppoe-connection-windows-10
• http://stackoverflow.com/questions/14614465/establish-a-vpn-connection-in-cmd