You might be able to assign a schedule value directly to the EMS actuator.

Schedule:File,
    SchName,  !- Name
    ... (all associated Schedule:File object's fields)

EnergyManagementSystem:Actuator,
   YourActuatorName,   
   SchName,       
   Schedule:File,     
   Schedule Value;

Yes, you need a small EMS program with a line that sets the actuator equal to the sensor.

Ivan's answer is misleading. Schedule:File should be a Sensor, not an Actuator. Some parameters you want to override in Schedule:File should be Actuators.

One example. I wanted to override the Outdoor Air Drybulb Temperature for building surfaces with Schedule:File for some reason. In such cases, the EMS program looks like this:

Schedule:File,
    Surface_Temp_Hourly_Profile,  !- Name
    ,                        !- Schedule Type Limits Name
    C:\Project\Project_XXXXX\Surface_Temp_Hourly_Profile.csv,  !- File Name
    2,                       !- Column Number
    1,                       !- Rows to Skip at Top
    8760,                    !- Number of Hours of Data
    Comma,                   !- Column Separator
    No,                      !- Interpolate to Timestep
    60;                      !- Minutes per Item

EnergyManagementSystem:Sensor,
    Surface_Temp_Hourly_Profile_Sensor,  !- Name
    Surface_Temp_Hourly_Profile,  !- Output:Variable or Output:Meter Index Key Name
    Schedule Value ;         !- Output:Variable or Output:Meter Name

EnergyManagementSystem:Actuator,
    Surface_OA_Temp_2to50F_Office_1_Floor,  !- Name
    2to50F_Office_1_Floor,  !- Actuated Component Unique Name
    Surface,                 !- Actuated Component Type
    Outdoor Air Drybulb Temperature;  !- Actuated Component Control Type

EnergyManagementSystem:ProgramCallingManager,
    EMS_PCM_Surface_OA_Temp_Override,  !- Name
    InsideHVACSystemIterationLoop,  !- EnergyPlus Model Calling Point
    EMS_Program_Surface_OA_Temp_Override;  !- Program Name 1

EnergyManagementSystem:Program,
    EMS_Program_Surface_OA_Temp_Override,  !- Name
    SET Surface_OA_Temp_2to50F_Office_1_Floor = Surface_Temp_Hourly_Profile_Sensor;  !- Program Line 1

Output:EnergyManagementSystem,
    Verbose,                 !- Actuator Availability Dictionary Reporting
    Verbose,                 !- Internal Variable Availability Dictionary Reporting
    ErrorsOnly;              !- EMS Runtime Language Debug Output Level