Creation of data import profiles happens in the data import settings. These settings are available to a limited number of LTS staff.
Creating profiles: https://wiki.folio.org/display/FOLIOtips/2-Creating+and+using+profiles
Understanding MARC and other mappings can be an important part of successfully administering data import and export: https://wiki.folio.org/display/FOLIOtips/MARC+Mappings+Information