Toolbar : 
Geometry toolbar 


Menu : 
Add menu > Geometry submenu> > Add Circle 

What to do : 
The Circle is now in the graphicarea. 

FreePoints or MergedPoints Add the centrePoint as a:


Notes : 
A Circle is a SketchLoop. A Circle is the most basic shape of a CamFollower. 

Top tip : 
Add the Dimension before you add other constraints. The centrePoint may collapse to zero radius if you add a constraint before you add a dimension. 
Example 
How to Add... 
SelectionWindow 


Drag

Circlen + Pointn at the center 