Using-pepcli.md

@@ -172,7 +172,18 @@ The `castor` command's various sub-commands are used to interact with PEP's [Cas
 
 ### `castor list-import-columns`
 
-@@@ more here @@@
+This command lists the columns that may be needed when the specified Castor data are [imported into PEP](https://gitlab.pep.cs.ru.nl/pep-public/user-docs/-/wikis/Castor-integration#import). Since the import process cannot create columns itself, Data Administrator must create required columns beforehand. This command is usable to find out which columns are needed. The command must be invoked with the `--sp-column` switch, specifying the column containing short pseudonym values that correspond with the Castor study's record IDs. E.g.:
+
+```
+pepcli castor list-import-columns --sp-column ShortPseudonym.Visit1.Castor.HomeQuestionnaires`
+```
+
+While the output lists the columns that will be needed by the import process, this command does not create them. Use the [`castor create-import-columns` comamnd](castor-create-import-columns) instead to have the columns created instead of just listed. Alternatively, Data Administrator can `castor list` the columns, then use [`ama column create`](#ama-column-create) and [`ama column addTo`](#ama-column-addto) to create them and group them into the `Castor` column group.
+
+The `castor list-import-columns` command accepts two optional switches:
+
+- the `--xml-structure-file` switch can be used to work around a Castor bug that prevents `pepcli` from being able to list import columns when PEP is configured to import Castor survey data, and there are survey packages containing more than 10 surveys. For such situations, the Castor administrator should [export](https://helpdesk.castoredc.com/article/170-export-and-import-the-form-structure) the survey package structures from the Castor Web interface, which yields an XML file. The path to this XML file must then be passed to the `--xml-structure-file` switch to allow import columns to be listed.
+- the `--answer-set-count` is used for Castor studies containing surveys that are answered multiple times by participants. PEP imports such survey data into [numbered columns](https://gitlab.pep.cs.ru.nl/pep-public/user-docs/-/wikis/Castor-integration#column-naming), and the switch indicates the number of answer sets to expect. For example, if participants will answer a survey a maximum of 10 times, specify `--answer-set-count 10` to have the command list sufficient column names for all survey answers to be imported.
 
 ### `castor create-import-columns`