You can access this dialog by using the Packages button in the Global Options\Basic Package dialog. This dialog is used to specify which packages are to be used in the simulation. The check box to the left of the package name is selected to signify that a package will be used as part of the simulation. One of the flow models and one of the solvers must be selected. Each of the boundary condition/source/sink packages is optional.
Some of the MODFLOW 2000 process have other prerequisites. The sensitivity process requires that there be observations. The parameter estimation process requires the sensitivity process.
Changing individual processes may change the Run Options in the Global Options\Basic Package dialog.
Related Links:
Packages Supported in GMS
Importing an Externally Defined Simulation