Beatriz,
Which part of the help is not clear? If you can explain what settings you have made so far, we can try to point you in the right direction. Are you testing this out in the standard planning book/ data view?
Planning Area
Planning Book / Data View.
Settings in SNP2 tab of product at warehouse
ATD Receipts and their ATP categories
ATD Issues and their ATP categories
Shipping / Receiving Calendars - test without using them
Settings for real-time deployment
Regards
AK