Assuming that the files are shared with the correct permissions
on the work server side and that the incoming VPN connection is already set up which should be done by the network admin. Virtual Private Network (VPN) - Enable Incoming VPN Connections
How to set up the correct permissions for VPN sharing. Sharing and Permissions
And you forwarded these ports on your router's firewall. PPTP TCP Port 1723
PPTP GRE TCP/UDP Ports 47
From what I have read you may also need to go to ipv6 properties of the VPN connection and uncheck' use default gateway on remote network.
You may also need to use the UNC path to access the folders or drive, though I believe the User name and password would usually work \\hostname\sharename