How to take mucinex for cold?

My dr always would recommend taking mucinex when I had a bad cold or sinus infection and idk why but I would never do it. Well I’ve had a cold now I’m on day 6 and I took mucinex the first like 3-4 days and my mucus has definitely thinned out but do I keep taking it until it’s gone? Also we have been home and we’re all losing my mind. Are we probably not contagious anymore? My LO has dance class today and I’d like to take her but idk we still have some lingering symptoms. It’s not covid.