I found two tutorials:
1) https://wiki.scribus.net/canvas/Your_fi ... th_Scribus
Note that this tutorial was last edited on 14 January 2011 and is based on Scribus 1.3.3.10 or above.
The interface may have changed and I could not complete the tutorial in 10 minutes .... maybe bcz of lack of time and patience ....

2) https://www.lollyjeanne.com/create-edit ... d-scribus/
See also viewtopic.php?p=70585 ( PDF Forms Designer, requires Java )