When importing events via .csv, you can import recurrence rules for these events.
You do so by adding a column labeled RRule in the .csv file to be imported. Then for the event series, specify the recurrence rule in that column.
It can be a bit tricky to know how to specify a recurrence rule for import.
The repeating values for importing events follow the RFC 5545 iCalendar standards. Seeing as that document is a little complex, here's an easier way to find out how to specify the repeating pattern you want for an import.
Use a "Test" sub-calendar for this method, and deactivate it when done. Or, you can use a live demo or create a new Teamup calendar for testing.
Open the exported file to see how the recurrence rules (and the column name) are specified. Then you can copy and paste the needed recurrence rules into your .csv file for import.