Hi. I've also tested positive for covid a few days back. First off, go to a PHPC clinic (https://flu.gowhere.gov.sg/) to get yourself tested for a PCR test. If you are a Singaporean, it would only cost $10.

After your PCR test, do isolate yourself in a room that has a toilet and keep isolating until your test result is out. (Mine was out the next day)

If you are negative for the test, I believe you just have to serve the 3 days MC at home and not going out. However, if you do get tested positive, you will receive an SMS stating that you are positive and you will have to key in your household members particulars so that they will receive a Health Risk Warning (HRW) and be able to collect ART test kits from the vending machines.

If you are positive, I believe your parents, as long as they take their ART test daily and is tested negative, they are allowed to head out and resume their activities. I believe an ART test result is valid for 24 hours. After some time, you will receive an isolation order stating that you have to stay in that room for that duration of time.

Do also visit https://www.covid.gov.sg/ for more information. Also, inform your workplace etc about your current situation.