what does it mean to torque the spacers? does it mean to tighten the bolts with a machine wrench?

^ lol.. it means to torque them. Your know torque~

if i drive my car every day. when should i retorque the wheel spacer nuts and wheel nuts? once a month?

Generally people say torque them when you install them and after 500 miles or so. Checking on the torque every once in a while isn't a bad idea though.

Use a torque wrench at 80 ft.lbs. Torque lug nuts using a star pattern.