Double click your object to get into node edit. Press "O" on the keyboard and will make a perfect circle plus add nodes to it.
If you are making a flange make the two circles (ID and OD). Select both and press C then E (center and even) and do a ARRANGE/MAKE PATH. This will make the flange one piece. Then generate one bolt hole or whatever you are wanting around the flange and select all (ctrl + a), do a C and E again. Off click, then select the item you want around the flange. Go to LAYOUT/ARRAY. In the upper left is a drop down. Change to ON ARC. Enter the radius you want along with total and will evenly draw out whatever you are putting around the flange.
Let me know if this isnt clear enough...
