The technical details of how MCMC programs generate these values are beyond the scope of ModelAssist: the book by Gilks et al (1998) is an excellent reference, though a little tough going. The user interface, where we write the stochastic relationships between the variables, is quite simple. The WinBUGS software (freeware: www.mrc-bsu.cam.ac.uk/bugs/ ) has become the effective industry standard for carrying out MCMC analysis.
free WinBUGS and JAGS software were among the first platforms to perform MCMC analysis. More recently STAN has become a popular, more flexible choice that is well supported and offers an easy interface with other free statistical packages such as R and Python.
When using a spreadsheet model, the easiest way to connect the The great benefit to Crystal Ball users is that the data (random samples from the joint posterior distribution for the estimated parameters ) from WinBUGS can be exported into a spreadsheet, which can be directly resampled for a Crystal Ball simulation. from an MCMC package is to import them in tabular forms (i.e. one column per parameter) and then resample them in pairs using your MC platform of choice. For example, in the @RISK software this can be easily accomplished using the RiskResample function.