Circles are really easy, you just need to use sine and cosine (which you don't have to understand, but it helps if you do).
Generally, if (cx, cy) is the centerpoint (e.g. the object to revolve around), and t is time (e.g. in frames or ticks), and r is the radius (e.g. in pixels), you can calculate the (x, y) coordinates like this:
x = cx + r*cos(t)
y = cy + r*sin(t)
You can adjust it in places to make it faster, slower, more like an oval, etc.