I pay quarterly. Whether you work a W2 job or not you're gonna owe unless you either increase your withholding to cover SE tax and tax on shopping income, or pay estimated tax.
If you go to irs dot gov and select pay then tax withholding estimator it works kind of like an app and can be used to calculate what you owe. I just recently found it so I can't say how accurate it is. I'll find out next year as I saved the result to compare to.
In any case, ignore me and talk to a tax pro.