This depends on how you set up your virtual network. Which mode are you using? I assume you are using the default (NAT). In that case you'd have to set up port forwarding. Or you could switch to the bridged or internal networking modes.
read more about it at these links
I think the "Host-only" adapter deserves to have a little bit more attention. After all it is a very important network adapter in the VirtualBox world, in particular when installing Oracle Databases. For instance, it allows any guest OS to use a fixed or automatic TCP/IP addressing according to the range defined by the VirtualBox "vboxnet" adapter. However, and this is were all documentation I have seen so far were unclear to me, any guest OS installed on the same computer must use the IP address of the "host-only" adapter (192.168.56.1) to connect to services provided by the host OS, instead of the actual or real IP address of the host OS.
The VirtualBox forum might actually be a more suitable place to discuss VirtualBox setup questions.
To the original poster: What are you actually trying to accomplish? Do you need to know how to enter an IP address in Putty or how to use it with X Window client software. What is your concern or problem? Please be more specific.