How can you help an elderly loved one who is overheating?

Take to ER now. Hyperthermia is medical term for overheating. It can range in severity from heat exhaustion to heat stroke. To be on safe side, since you've mentioned no other details, take your loved one to ER now for evaluation & appropriate treatment. Check out http://www.medicinenet.com/hyperthermia_symptoms_and_signs/symptoms.htm for some basic info.