A subset is just a group of addresses taken from the range of addresses being used by your local network clients (usually, the scope of addresses assigned by your DHCP server). For example, if the local network is using addresses in a range defined as 192.168.1.20 to 192.168.1.50, you might assign addresses 192.168.1.30 to 192.168.1.35 to remote access clients.

Of course, there are other factors that could be causing you to not be able to "see" or connect to network resources, such as network browse issues, DNS issues, etc.