We just went through this a few months ago, my kids got it from a kitten we adopted. It was a nightmare and we spent almost $350 on treatment for both my kids, the cat, and our dog who she also gave it too.
Ringworm will be in the system for about 10 days before it starts to show up. It will look like a red circle for a few days, could be mistaken for a bug bite or rash, then the center of the circle will heal to normal skin, that may be somewhat scaly, and the red ring will remain. Some people experience itchiness or blisters, my children's many ringworm spots were not itchy/blistery at all, just lightly raised red spots that eventually turned into the tell-tale ring.
Looots of cleaning, literally, scrub every hard surface and wash every cloth surface, b/c the fungus spreads all over due to it's tiny spores. If it is on the skin, then a simple over the counter anti fungal treatment will heal it. It takes 3 days of meds before it is no longer contagious, so for the first few days it needs to be covered with medicine and a band-aid. After that, you have to do the medicine for about 4-6 more weeks to really get it. If the ringworm is on the scalp, hairline or head, then you must go to the Dr. to get prescription oral antibiotics, because creams don't work in that type of hair and your child will be left with a bald spot permanently.
Many people only get one or two spots, so fairly easy to treat. My kids had over 24 spots, plus in their hair... they played and slept with the cat, and kept getting reinfected over that 10 day dormant period. Oh, we had to treat and quarantine the animals for almost 2 1/2 months. Royal nightmare.