The problem you are describing is a basic requirement of being a competent, certified IT engineer, if you don't already know how to use group policy, remote access, and endpoint protection, you should not have a job in an IT role where you are solely responsible for the maintenance of computers!
I would highly suggest taking night school classes at a local university to learn enough to properly manage the system.
For now, contact the computer manufacturer (likely dell or HP) and see about purchasing a turnkey solution with remote access and an endpoint virus protection already set up for you.