First of all, you can check this article, thanks to the author:
http://abool.blog.51cto.com/8355508/1575399
Here are the keys to success
1. Three services need to be installed in the server manager, network policy and access, web service (iis), remote access, and routing must be selected when installing remote access.
2, After the service is installed, configure the static ip pool, and the ip address can be customized, but it should be configured according to the connection method with an unoccupied ip.
3. After adding the user, you can actually access it, but you are accessing the internal network. You need to set the NAT address to refer to the external network.
4. Log in to vpn by creating a connection, and the ip is the public network ip of the server.