Very wide viewfinders today have no swing or tilt adjustment, which was common on even 35mm finders in the past.
The previous post said frame for 1/4 from top, I have experienced that within 3 feet or so 1/2 from the top is in order and swing the camera 1/4 frame to the left.
Very wide viewfinders are good for architecture and landscape and lining up vertical and horizontal. The viewfinders ar pretty good when 10 feet + from your subject.
I almost never use one. To get the hang of it and if you don't have a digital camera, imagine a small compact car and step back 5 steps, at that distance you will have the whole car in the frame.
When framing without the add on viewfinder, the center is still the center, so it's pretty easy to adapt, but remember you are still framing for a large area above and below, as well as right and left. So if you don't want a bunch of sky the option is for a big bunch of ground!
I only needed 3 test shots with a digital to get the idea, so it's really not that hard to adjust.
21mm shot without a viewfinder. I got it all in with one take!