The best treatment for this is to apply antibiotic to the area when you can. You will have to get this from the doctor from a prescription. Go see a doctor and get the area checked and see what the intensity of the infection is. Based on that you will get a prescription.
Although you can go out without getting a prescription and buy ringworm ointment and medication, it's best if you see your vet right away to get pills that will help kill the ring worm faster.
There are a couple of treatments to do for ring worm infection but the best way to go about it is to apply anti fungal agents. Applying it to where the dog is infected by ring worm.
