There are several ways to record a program.
Make sure that your modem and decoder are switched on (standby mode is sufficient for the decoder).
Your recordings will be stored for 60 days as standard. You can change that time frame before the recording starts. It is not possible to do so afterwards.
You can see how many days a recording will still be stored: press and select:
In the list of recordings ( or next to the title of the recording, depending on your TV menu), you will see the number of days during which it will still be available.