How do I go about setting up a payment plan?

Payment Plans Installment Agreements | Internal Revenue Service (irs.gov)

scroll down to the area you are asking about, 

You can fill a form 9465 out a installement agreement request  and additional info is 75% down the page

This help article will direct you to the IRS site where you can apply.   If you owe state as well, they have their own system that you will need to navigate.   You can find your state's tax agency here.  

Go to IRS.gov and search Installment Request