I made purchases from two different companies. They are stating I may be required to remit "use tax" to the PA Department of Revenue. What should I do?

A "use tax" is a tax that most states collect nowadays. It is the sales tax on items that you bought out of state and on which no PA (in your case) was collected (I assume you live in PA).

In the Pennsylvania interview, you will come to a screen with the heading "Untaxed Out-of-State Purchases". Answer "yes", and then answer the questions on the following screens.