How to use a trained neural network model?

I can not understand how to use the already trained neural network model. I program on python, I use library keras. I analyze the time series. The neural network is trained, the model is saved.

As described in the keras documentation, you need to call the model_name.predict () method. Good. I do this: model.predict (dataset), where dataset are the values ​​for the last 90 days. And I need to get a prediction forward for, say, 10 days.

But the forecast is made only for the specified data set for 90 days! That is, you can only compare the original data and forecast.

So how do make a forecast for 10 days in advance from today?