Start by opening "Financial"

Then click "Accounting" on the left side.
Then click "Posting journals"
You can also search for "Posting journals" by clicking the search field in the upper left corner.

NOTE: if you cannot find "Posting journals", it is because you lack permission for it. In that case, you can contact support to get access.
Select the journal you want and click "Edit"
Check "Automatic posting"
REMEMBER to finish by clicking "Save"
Want to know more?
Read more in these related articles:
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This article explains how to enable automatic inventory posting for stock journals in Sapera
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VAT reporting - automatic
This article explains how VAT reporting is performed automatically via the Danish Tax Agency's API in Sapera