[Patrickwhite]

If you are referring to the default dashboard as opposed to ZomB or one of the other community dashboards, then you are in for a rough time. There is no documentation provided (as far as I am aware) and the example code is brutal.
From FIRST's DashboardExample.java:

void updateDashboard() {
        Dashboard lowDashData = DriverStation.getInstance().getDashboardPackerLow();
        lowDashData.addCluster();
        {
            lowDashData.addCluster();
            {     //analog modules
                lowDashData.addCluster();
                {
                    for (int i = 1; i <= 8; i++) {
                        lowDashData.addFloat((float) AnalogModule.getInstance(1).getAverageVoltage(i));
                    }
                }
                lowDashData.finalizeCluster();
                lowDashData.addCluster();
                {
                    for (int i = 1; i <= 8; i++) {
                        lowDashData.addFloat((float) AnalogModule.getInstance(2).getAverageVoltage(i));
                    }
                }
                lowDashData.finalizeCluster();
            }
            lowDashData.finalizeCluster();

            lowDashData.addCluster();
            { //digital modules
                lowDashData.addCluster();
                {
                    lowDashData.addCluster();
                    {
                        int module = 4;
                        lowDashData.addByte(DigitalModule.getInstance(module).getRelayForward());
                        lowDashData.addByte(DigitalModule.getInstance(module).getRelayForward());
                        lowDashData.addShort(DigitalModule.getInstance(module).getAllDIO());
                        lowDashData.addShort(DigitalModule.getInstance(module).getDIODirection());
                        lowDashData.addCluster();
                        {
                            for (int i = 1; i <= 10; i++) {
                                lowDashData.addByte((byte) DigitalModule.getInstance(module).getPWM(i));
                            }
                        }
                        lowDashData.finalizeCluster();
                    }
                    lowDashData.finalizeCluster();
                }
                lowDashData.finalizeCluster();

                lowDashData.addCluster();
                {
                    lowDashData.addCluster();
                    {
                        int module = 6;
                        lowDashData.addByte(DigitalModule.getInstance(module).getRelayForward());
                        lowDashData.addByte(DigitalModule.getInstance(module).getRelayReverse());
                        lowDashData.addShort(DigitalModule.getInstance(module).getAllDIO());
                        lowDashData.addShort(DigitalModule.getInstance(module).getDIODirection());
                        lowDashData.addCluster();
                        {
                            for (int i = 1; i <= 10; i++) {
                                lowDashData.addByte((byte) DigitalModule.getInstance(module).getPWM(i));
                            }
                        }
                        lowDashData.finalizeCluster();
                    }
                    lowDashData.finalizeCluster();
                }
                lowDashData.finalizeCluster();

            }
            lowDashData.finalizeCluster();

            lowDashData.addByte(Solenoid.getAll());
        }
        lowDashData.finalizeCluster();
        lowDashData.commit();

    }

Baffling and undocumented. I would look to the community dashboards.