I was able to make this round edge and it’s exactly what I want, but it doesn’t always work.
As seen in the screenshot, I use the circle tool and delete the 3 unwanted quarters and push down the model. But sometimes I cannot delete the unwanted quarters without deleting the whole thing. Not sure why it works… sometimes.
Why can’t I click on an edge and just bevel it
Your screen shot shows that the arc does not intesect with the corner or the top edge of the rectangular face. You’ve drawn it outside the component/group. You need to have the component/group open for editing BEFORE drawing the arc.
No need to feel dumb; we’ve all been there, especially in the early days learning to use the software. It also reminds me that the most stupid question is the one never asked!