The urban are urbanised, the urbane are ?
The process you are describing essentially means bringing someone into a particular culture, with emphasis on qualities that are deemed polite, etc. When applied to a hypothetical tribe of nomads, the implicit assumption is that the tribe's own culture is rude and uncouth, and that the "urbane" culture is proper and superior. Depending on how you feel about that assumption you might want to use different words.
- Educated, educating: The tribe was educated in proper manners, etc.
- Re-educated
- Assimilated
- Colonized
- Civilized
- Acculturate