Also devices connected via VPN provide normal TCP / IP connections externally. Devices necessary for access do not need further software. You use IPv4 address, which you get for establishment of VPN.
Devices, which shall become achievable, need client software "openvpn".
This is available for every platform. It will be installable with distribution repositories directly if you use "Linux" system.
deb based system with sudo apt-get install openvpn
rpm based system with e.g. zypper install openvpn
If you use Window, you can download openvpn via openvpn - hompage. (Link)
After establishment of VPN in your account of our websitey ou get a zip file, which you need to extract to configuration register of openvpn. Now every settings are already deposited in files. Tunnel is ready for use after reboot of software.
TIP: If you use Windows, you need to start with installed opnvpn-gui via administrative privileges. If your tunnel shall be active right after booting up automatically, you have to activate this for openvpn.
It is very simple to access devices behind VPN target when using Linux, e.g. access to RDP server behind VPN system:
iptables -t nat -A PREROUTING -p tcp --dport 3389 -j DNAT --to 192.168.1.2:3389
iptables -t nat -A POSTROUTING -j MASQUERADE
We will publish further how-tos in forum soon.