Presumably these are all Text fields? If you set Index Fields in the priority order you wish (highest-priority first), and under Search Settings set Position in Text to max (and preferably lower the other rank knobs), then hits in the first Index Field will rank higher than hits in the second, etc. all else being equal (e.g. all terms found).
Note that it may take several minutes or more (on a large profile) for Index Fields to be updated, as the index needs to be rebuilt. Note also that this will not guarantee that hits are in Index Fields order; e.g. if both query terms are found in the second Index Field and only one in the first, the hit in the second Index Field may be shown first, because finding all terms of the query still ranks higher than Position in Text scaling.
