What platform are you on?
Judging by your bug report, I think you're playing on Windows. So, you'll have to take a screenshot the way your system allows. I don't use Windows, but hopefully
this wikiHow guide is helpful!
On a Mac, you'll have to use Command+Shift+3 (for the entire screen)
or Command+Shift+4 (for a restricted area).
Same deal with Mobile, you'll have to use your system's function.
If you're on Switch, you can use the screenshot function (the circle-in-a-square button on your left Joy-Con). It will be added to your Album, and you can use the Send to Smart device function to get it onto your device. A detailed guide
here.
If you're on Xbox, then unfortunately I think you'll have to take a photo of your TV screen with a phone, because (unless I'm wrong), Xbox doesn't have a screenshot feature.
To get it on the Forums (if that's desired), then you'll have to either drag and drop it in or use the Insert Image function.
Hope this helps!