How is an exhaust tip welded on?

Hello, I am putting a new exhaust tip on my car. It’s currently a 2 inch pipe. I am looking to buy a 2 inch to 3 inch chrome exhaust tip.

My question is: when I weld it, how do I do that?

Do I buy a 2.5 inch pipe that sticks over my current one, then weld it on.

Or do I buy a 2 inch and press it against my current pipe and weld it that way?

Thanks in advance