Is this for a Mechanica study or a MDX/MDO analysis? Depending on what your goal is, the answers will be very different. Is it a ball bearing, a needle roller bearing or a bushing that is supporting the shaft?
OK, good - I have an excellent reference at PTC's website that will address your problem pretty closely:
It does assume that the support is an ideal "point" support, but it's a pretty good approach to simulate a shperical bearing support. I think it will do a nice job for what you'd like to accomplish, short of modeling the shperical rolling elements and races in detail.