Trouble drawing a static magnetic field around a single looped wire

I've been stuck on this problem for a while, and I haven't been able to tackle the problem. Basically I'm supposed to draw field lines around a looped wire (circle). I've been using polar coordinates in order to try plot something down however I think the way i'm apporaching this problem Is wrong. How do you actually plot field lines around an object? My understanding is quite limited so any help would be greatly appreciated!