How does someone know if they have a concussion? And should they sleep it off? Are that's a bad idea? And can they take tylenol (acetaminophen)?

Confusion/headache. A concussion can occur after impact to the head and can cause loss of consciousness. Confusion can be an early symptom. Headache also can be a problem. If someone has enough impact to their head to cause either severe headache, nausea/vomiting, confusion, passing out, or seizure they should be evaluated at a hospital. They may need to be monitored in the hospital until these symptoms resolve.
Depends. The effects of concussions can vary and be unpredictable. It depends on the severity of the injury. The best thing is to give your brain complete rest. The more stain you place on your brain while it is attempting to heal, the more likely it is to slow down the healing process. Tylenol can be used to treat the headache.