To write a report for joint private clients (e.g. Mr & Mrs Smith) go to write / view report, and add both clients individually in turn to the Selected Client(s) list and click write report.
The first client you add will notionally become the 'primary' client and as such their details will be displayed first throughout the report
If one or both clients are existing clients, you can locate and select the client(s) using the client search. If one or both clients are new clients, you will need to add them using one of the three add new client buttons. This will not only automatically add them into the Selected Client(s) list, but will also save them to the selected user's Client Library for future use.