Choose the Arc By Center Point command 
.
Click where you want the center point to be (A).
Click where you want the sweep of the arc to begin (B) and end (C).
Tip:
You can change the arc direction by moving the cursor.
Tip:
Instead of clicking to define the radius, you can type a value on the Arc command bar. You can also use a combination of graphic and command bar input.
IntelliSketch places relationship handles.
You can use the boxes on the command bar and the commands on the shortcut menu to edit an arc.