You will need to install SQL Server again for the new instance. You will need a Virtual Server Name (A unique name used to identify the virtual server on your network) You will need a static unused IP address to identify your instance. You will also need a minimum of 1 shared disk to keep your data files.
Yes, you can use existing setup to do that. You have to install SQL Server as a named instance. You also have to configure SQL Server cluster resources: ( physical disk, Ip address, shares and etc.) and dependencies. KK