For each circle I set the OLFA to the correct radius of the circle. I then drill a 1.5mm in the center of scrap card that's larger than the circle I'm cutting. I then put the card over the pin tubing of the MDF/matt board and hold it in place with a finger or two. Next I place the OLFA in the tube and rotate it part way around, cutting part way into the card. I release the card and "unrotate" it as well as the OLFA. I continue to cut and unrotate until I've gone around the circle enough times to cut all the way through and TAA DAA! A NICE CLEAN CUT CIRCLE! When making a ring I simple readjust the OLFA to the correct inner radius cut out the inner circle the same way.
My explanation may make the process seem awkward but it's actually quite simple: Once the OLFA has been set and you've got a stack of card pieces with 1.5mm holes in their centers it takes very little time to cut out a bunch of circles/rings.
WHY GO THROUGH ALL THIS? 1) The pin tube really helps the cutter and card rotate with minimum difficulty and 2) Turning the cutter all the way around the circle in one go is quite awkward, especially when cutting small circles. By only cutting part of the circle at a time it is much easier AND minimizes blade wear and tear.
HINT: When cutting circles out of matt board or balsa/basswood sheet, remove the jig's matt board and put the material directly over the tubing. Once you've cut the circle almost all the way through, flip it over and finish the cut.