make sure that each box has a unique license
On the box that will be the secondary do the following
Go to System Administration > Operations > Local Operations > Deployment Operations
Enter IP address of Primary Instance and admin username / password and then press "Register to Primary"
Regisration process takes a little time since also involves copying the database from the primary and then restarting the secondary with the new database. You can monitor the progress of this on the primary at
System Administration > Operations > Distributed System Management
