Replying to Sketchup

Not sure if this goes here, anyway

How do I make an arc shape a solid. For example if I'm making a tabletop jump, I want to round the landing so that its not / meeting a - , but rather a smooth curve. I messed around with it but I can't figure it out.

What I tried was making an arc so on the the side, pasting it to the other side, then deleting the edge remaining so it's just the arc. But from that point I'm lost, as the jump is solid on all other sides, but I can't get Sketchup to fill the area in between the 2 sides.

I'll try to get an image of what I'm doing but I think it makes sense?