When adding a property, you have the option of selecting the property 'type' and then entering in the # of units associated with that property. VerticalRent will automatically create the # of units you specify when adding a property. Of course, you will have to fill in the details of each unit afterwards.
To add individual units to a property, you can either do it from the 'Properties' tab under Quick Actions (on the right), or you can add a unit by clicking on the 'Add Unit' under Quick Actions anywhere in the Properties area. A small pop-up window will appear asking you to select the property and add the unit. Remember, you must always associate a unit with a property.