For dimensioning the diameter of a circle:
6. Start the Auto command.
7. Place the cursor over the circle to show its dynamic highlighting and display the character . Left click to confirm the dimensioning:
8. Choose the location of the dimension:
9. Left click to fix the chosen location of the dimension:
Pictures in topic were made with wrong dimension style, not Standard, real picture will be slightly different.
For dimensioning the diameter of a circle using characteristic points:
1. Turn on the Quadrant snap.
2. Start the Auto command.
3. Place the cursor over the circle to show its dynamic highlighting and display the character . Left click to confirm the dimensioning:
Mistake in 3 - you don't need left click to confirm the dimensioning, just follow to next.