Hi
You need to install the Remote Desktop role and get the licence for that role (RDS CAL)
On a server in a workgroup you need Per-Device RDS CAL.
You can't use the wizard, you need to add the RDSH's role and the RDP licensing service.
To give a small how-to;
On the workgroup computer install the Remote Desktop Licensing role service and the Remote Desktop Session Host role service. To do this, follow these steps:
Open Server Manager.
Click Manage and select Add Roles and Features.
Select Role-based or Feature-based installation.
Select the computer as the destination server.
On the Select server roles page, select Remote Desktop Services.
On the Select role services page, select the Remote Desktop Licensing and Remote Desktop Session Host role services.
Continue the installation. Select default values for the remaining settings.
Please be advised;
Configuring RDS on a workgroup server creates the following additional restrictions:
You must use per-device licensing instead of per-user licensing. For more information, see License your RDS deployment with client access licenses (CALs).
You must use Windows PowerShell to manage the RDS role services. This is because the Server Manager tools for RDS do not work. For more about using PowerShell cmdlets together with RDS
Thanks
Philippe