How do I change the resolution of circles in Sketchup

From here:

when you first draw a circle, type "48s [ENTER]" for 48 sides. or click on the circle and open the Entity Info dialog box. You can not change the divisions once you pull it to a cylinder though.

Try the 90s rule...

Create a circle by entering 1.0" and press return. Now type 90s & press return. You have created a circle with a diameter of 2", and told Sketchup you want 90 sides. This turns it into a complete circle. You should see the difference. Once you do this, all other circles will have 90 sides, within your current project, regardless of size. It has a memory.

If you export into CAD, you will want to do this 90s with all circles. Otherwise, your CAD (BobCAD) program will likely not recognize it as a circle. This is important for any drill routines, as you will want to place a center dot inside each circle, to specify the drill's (geometry) center location(s).