See the following help files:
predict.marssMLE() Predict and forecast.
forecast.marssMLE() Forecast. Use predict.marssMLE() to call with argument h.
plot.marssPredict() Plot a prediction or forecast.
autoplot.marssPredict() Plot a prediction or forecast using ggplot2 package.
print.marssPredict() Print prediction or forecast. If h!=0, i.e. forecast, only the forecast is printed but the marssPredict object (in pred) has all the historical time steps also.