What is the purpose for the Federal Government to apply tariffs on imported goods?

The general purpose is to protect local industry from the competition of cheaper imports. Through tariffs you can make them as expensive or even more expensive than local products.

The downside of this policy usually is that the countries hit by those tariffs then set up similar tariffs for your export products so that you end up protecting some of your local companies, but badly hurting others. This happened for instance during the years of the Great Depression, and it caused world trade to almost come to a halt.

Another purpose of protective tariffs is to control and limit the flow of local money and income that goes to other countries: the money paid for foreign products will not remain in your country's economy, but ultimately go to the country of the producers. Plus, corporate tax income from those companies paid to the State will not be income for your Government but for the Govenment of those other nations. This is an important reason for foreign producers like car makers to start manufacturing locally: of course part of the profits still go to the country of origin, but the companies' activities then support the local economy at a much higher level and they generate much more tax income for your own Government.