As an IC who got a sign on bonus in January, do I pay quarterly taxes on this? How much and to where? Employer said this will be on a 1099 at end of year.

I am a physician that officially started working in August and my sign on bonus is 4k per month starting in Jan 2019 (thus has had 3 4k payments to me). I will get this through June.   Employer said income will be reported on a 1099 for 2019. No idea what/where to pay.