Layout > Working with Entities > Creating Entities > To Create Fillets
  
To Create Fillets
1. On the Design tab, click the arrow next to Fillet and then click Circular Trim or Elliptical Trim.
2. Select a start point on a line, arc, or spline.
3. Select an endpoint on a second nonparallel line, arc, or spline. The lines are trimmed and connected by a fillet. The value of the radius displays.
4. Middle-click to exit the tool.