The procedure for direct debits is the same as for bank transfers. For further explanations, please refer to the article Transfers / Payment runs.
Direct debits
Open Functions / Direct debits (menu: Finance > Banks > Direct debits).
...
Apply house bank assignment rules, complete any missing mandatory information and create files and postings.
Note: The rules for direct debits and payment advice notes are applied to the complete payment list. Maintain the corresponding settings in the master data under House banks and Payment transactions. You can adjust the automatic assignment to house banks by clicking on Edit assignment rules.
...
Further explanations can be found in the process described in detail under Transfers / Payment runs.
...