your 90 days, which is a report that you're 90 days continiously inside Thailand, it stops at the moment you leave Thailand and it starts at the moment you enter Thailand. You need to calculate the days by yourself to make the first 90 day report.
You, your landlord, the house owner or the house master need to report your address within 24 hours at local Immigration Office, this can be done by using the website or using the app for mobil phone, click on this picture on the website for further info: TM30 Notification of residency
And before each and every one is going to share their own experience about applying for a visa or for an Extension of Stay or maybe something totally diffierent than a Non Immigrant O-A visa, I close it down.
If the OP has more questions feel free to contact a Moderator to re-open this topic.