Attaching the stove pipe to a Fisher stove

Welcome to the forum Doug;
You didn't mention if the pipe comes out of the top of the stove, side, or rear. If it's a 6 inch out the top, Dura Vent still makes the short adapter with a damper in it that will sit right on top of the stove, fitting inside the collar. Sideways, you should drill 1/8" holes through it to secure the elbow or pipe. Use oil on the drill bit, and take your time. They drill fairly easily. Sheet metal screws start in and many times will twist off before threading the hole in the thicker collar. A self tapping machine screw is better if you don't have taps to thread it. If the pipe won't fit into the collar, you may have to over-crimp the pipe to get it in.
I personally drill 2 holes on the sides, then put a piece of pipe strap around the elbow if it's an adjustable multi-piece type. One screw in the back of the elbow keeps the strap in place. That way if the elbow ever comes apart, it is at least held together. If you can use a 90* solid elbow, go with that instead with just screws.

Duh, I see "welded to the top" in your question; sorry about that. Crimped end down, damper in pipe, best with 3 screws if you feel safer with earthquakes and what not going on. If you have straight up sections going to a ceiling support box, there is plenty of weight holding it down, and it's not going anywhere. Most codes call for 3 screws at each joint.