From the Toolbar: Find the Radial Dimension Tool icon on the Entity Toolbar (color coded blue) and Click on the tool. The tool is now active and ready for use.

 
From the Shortcut Key: The default shortcut key for the point tool is the letter "Shift + D, 4". Simply press the key and the tool will be activated.

 
From the Command Line: Type "dimension_radial" into the Command Line, at the top of the notification window, and press the Enter/Return key.

1. Click on the drawing to specify the center point of the dimension.

2.  Move the mouse and click to set the chord point. This is the chord point from which an extension line will reach. The distance between center point and chord point will be the radius measurement value.

3.  Move the mouse and click when the offset distance is as desired. This designates the positioning of the dimension text.

Reset:

To add a radial dimension using the keyboard, open the Tool Tab in the property tree.        

1.  Type the center point coordinates into the "Center Point" 3D Point Property Field found on the Tool Property Tree and press Enter to accept.

2.  Type the chord point coordinates into the "Chord Point" field and press Enter to accept.

3.  Type the offset distance data into the "Offset Distance" Scientific Data Field and press Enter to accept. The dimension text will be positioned at this distance away from the chord point.

Reset:

Tab: Auto Snap Enabled: enables/disables the auto snap feature. Auto snap automatically enables the end, mid, nearest and quadrant Entity Snap features.

Show Unit: Displays the dimension's unit within the dimension entity's text.

Escape (Esc): Cancels current tool and activates the default tool (Selection Tool).

Space: Resets this tool.