How do handle business quarterly taxes for a side business?

How do handle business quarterly taxes for a side business when I am also a w-2 employee of a company?

 

I work for a company and get a w-2.  I also sell products online and need to pay quarterly federal and state taxes on my earnings.  I buy products from a manufacturer and sell them through different e-commerce channels as well as through a few brick and mortar stores.  

 

I know I need to pay federal and state quarterly taxes I'm just trying to figure out how to exactly do that and how to also handle that as a w-2 employee.

 

My side business is an LLC that is a pass through entity to my regular taxes.