To be able to set up the VPN, at least one node needs to be reachable by an unchanging address of hostname. This is normally not the case with common DSL uplinks (they change addresses every day). To mitigate this problem and get a fixed hostname, there are services called dynamic DNS or short DDNS. There are lots of different DDNS services, some are free, some cost money. Most of those services provide a common API that can be used by freely available tools to update the address whenever it changes. Mainstream DSL routers have built-in clients for this API so nothing has to be installed to set up DDNS.
Besides this unchanging address, a port has to be opened for VpnCloud. This has to be done in the settings of the DSL router. The default port for VpnCloud is 3210. This process is different for every router but it usually can be found under the name of "Port forwarding" or "Exposed ports" (not "exposed host").