my csa 1099r comes from the OPM it is a monthly pension not from an annuity so there is no RMD and there box 2a says unknown, Turbotax how do i proceed?

RMD rules are generally satisfied through periodic payments made to you from your pension plan.

Required Minimum Distributions

In TurboTax, select YES to the RMD question (Was this withdrawal RMD and all of this was RMD).  

As for box 2a, please check the JamesG1 for detailed response.