Ok, so here is a brief explanation.
I suppose your computers at home are behind a router right? Which means you will have to forward (port forward) the port 1723 (that's the VPN port) towards an internal IP adress (i recommend this to be the Windows machine). Another important thing is you should have a static internet IP address given to you by the ISP. If you don't have a static IP address things are way more complicated.
Things you will need:
1. Your router has a static address for example 77.28.65.32 (which is placed on the router's WAN port)
2. Your Windows machine should have a private IP address for example 192.168.1.1 (should be set as static not dynamic so it is persistent)
3. Your router needs to be set up to forward the VPN traffic on port 1732 from the 77.28.65.32 to 192.168.1.1.
This means that when you initiate a VPN connection towards 77.28.65.32 it will end up on 192.168.1.1. This is what we want.
After this you need to set up your Windows machine to accept incoming connections. Google this (how to set windows accept incoming connections) issue and you will find what you need.
So first, post back whether you have a static public IP address or not. Then post back your Windows version and whether your private IP is static. Last, post the router model.
Good luck mate