To do this you need to use the DesignSpecification:OutdoorAir object. Note here that if you're doing this then you should remember that the system availability schedule controls the entire system - both heating/cooling and ventilation. If you want to only have heating available during the day (for example) you should set its availability schedule specifically in the heating availability schedule input rather than using the system availability schedule for that.
Most of the inputs below are just defaults - the key ones to look at are the availability schedules, the outdoor air method, and the design specification outdoor air object name.
HVACTemplate:Zone:IdealLoadsAirSystem,
Living1, !- Zone Name
, !- Template Thermostat Name
Always On, !- System Availability Schedule Name
50, !- Maximum Heating Supply Air Temperature {C}
13, !- Minimum Cooling Supply Air Temperature {C}
0.0156, !- Maximum Heating Supply Air Humidity Ratio {kgWater/kgDryAir}
0.0077, !- Minimum Cooling Supply Air Humidity Ratio {kgWater/kgDryAir}
NoLimit, !- Heating Limit
, !- Maximum Heating Air Flow Rate {m3/s}
, !- Maximum Sensible Heating Capacity {W}
NoLimit, !- Cooling Limit
, !- Maximum Cooling Air Flow Rate {m3/s}
, !- Maximum Total Cooling Capacity {W}
HVAC_day, !- Heating Availability Schedule Name
HVAC_day, !- Cooling Availability Schedule Name
None, !- Dehumidification Control Type
0.7, !- Cooling Sensible Heat Ratio {dimensionless}
60, !- Dehumidification Setpoint {percent}
None, !- Humidification Control Type
30, !- Humidification Setpoint {percent}
DetailedSpecification, !- Outdoor Air Method
0.00944, !- Outdoor Air Flow Rate per Person {m3/s}
0, !- Outdoor Air Flow Rate per Zone Floor Area {m3/s-m2}
0, !- Outdoor Air Flow Rate per Zone {m3/s}
mvent, !- Design Specification Outdoor Air Object Name
None, !- Demand Controlled Ventilation Type
NoEconomizer, !- Outdoor Air Economizer Type
None, !- Heat Recovery Type
0.8; !- Sensible Heat Recovery Effectiveness {dimensionless}
DesignSpecification:OutdoorAir,
mvent, !- Name
AirChanges/Hour, !- Outdoor Air Method
0.00944, !- Outdoor Air Flow per Person {m3/s-person}
0, !- Outdoor Air Flow per Zone Floor Area {m3/s-m2}
0, !- Outdoor Air Flow per Zone {m3/s}
0.35, !- Outdoor Air Flow Air Changes per Hour {1/hr}
Always On; !- Outdoor Air Schedule Name
@Jung what simulation tool are you using? Please mention it in the title or body of your post, as well as add a tag so that others can provide better help.