The script guides you though the selection of the appropriate route for performing a reduction. Possible routes are using an import control table to interpret FITS headers, choosing from a list of known detector setups or just supplying all the necessary information.
Using FITS headers is only possible if your data contains the correct information. If a table is not listed for your telescope/detector combination then you will need to create one. The contents of import tables are described in the help for the program IMPORT. Unless you (and perhaps your colleagues) are going to reduce large amounts of data from an unknown telescope then you should use the normal setup and data organization techniques.
If you do not choose a detector setup file or have none you will need to organize your data into different frame types (bias, flat, target etc.), so either use a naming scheme that allows you to distinguish between them using wildcard patterns or create lists of the names in files.
If you cannot select from any of the known detectors then the most crucial information that you require is a knowledge of where the bias strips are and the useful CCD area (if these are appropriate for the type of data you’re reducing). If you are sitting at an X display then the CCD geometry can be determined from within REDUCE. Otherwise you will need to determine these before running reduce.