For a non-DRIVE-CLiQ line module (power rating less than 16kw): You must connect Pin 1 of the X21 connector to a digital input on your control unit. You must then set p864 from the expert list of each drive object to read the specified digital input. So p864 = Control_Unit.r722.X.

For DRIVE-CLiQ line modules (power rating of 16kW or above), the unit can be enabled either from a SIMOTION unit, or via PLC: 

SIMOTION: Use the system function block _LineModule_Control. For a detailed explanation of this function block, see https://support.industry.siemens.com/cs/document/1...

PLC: Use the SINA_INFEED function block from the DriveLib library in TIA Portal V14 onwards. The DriveLib library can be found at https://support.industry.siemens.com/cs/document/1... if not already installed. Documentation on the use of this function block can also be found here.