[Gretl-users] arima forecasting

Hello, I'm trying to use an a raima model to forecasting. How to write a script that forecasts forwards some variable? I've dataset/file that includes "X" observations in time and i want to forecast this observation in time hour+1 or hour+2 forewards. How to do it? I know that I should to use "fcast" or "fcasterr" functions, but i don't know how to get time parameters. Please, help me. Best regards, walgula