I just want to make a Federal payment. What is the easiest way to do this? Thanks

online using IRS website - go there and click on make a payment. this allows payment for many different reasons such as estimate, balance due, payment plan etc. at the end print put documentation for the payment just in case you ever nee to refer back to it.

Here's the site to make a payment to the IRS:

https://www.irs.gov/payments