How can take off the air actuator, do I need to take off the dash board if yes tell me how

The answer is... maybe. I'm not familiar with your model of Nissan, but with some cars/trucks, you can gain access to the blend door actuator by removing the passenger air bag and reaching in through the dash. It may also require loosening the dash and rocking it forward enough to get at the actuator without fully removing the dash. You'll need to lookup your vehicle's make/model/year to know just where the actuator is. One potential problem when not removing the dash is that you can't gain access to the top of the screw heads holding in the actuator. A workaround for this is to remove the screws you can reach, and snap the old actuator out, leaving the rear screw in place, then cut slots into the rear screw holes of the new actuator and slide it into place. A dab of adhesive caulk can hold it in place after the front screw are tightened down. I guess you have to have a knack for working around trim panels and dashboards, a job like this can be daunting for a first timer but someone who has done several of these can get in and out fairly quickly.