If you have multiple monitors you would like to use when connecting to another machine via RDP client you must first make sure that are using the correct version of windows on both computers. Here is a list of the versions of windows which support this feature:
Windows 7 Ultimate
Windows 7 Enterprise
Windows 8.1 Pro
Windows 8.1 Enterprise
Windows 10 Pro
Windows 10 Enterprise
**Please note both computers must be using an operating system on the supported list above.
Once you know you have the proper setup, configuring Windows 7’s Remote Desktop multiple-monitor feature is easy. To begin, Launch Remote Desktop Connection and select the system you want to connect to with multiple-monitor support from the Computer drop-down list. Then, click the Options button to expand the Remote Desktop Connection window so that you can see all the tabs. Next, choose the Display tab and select the Use All My Monitors for the Remote Session check box, as shown in Figure 2.
To complete the procedure, return to the General tab and click the Save button.