A 1 dot retainer is built with the rules outlined in the ghoul book or appropriate entry for wraiths, zombies, spirits, vampires etc or anything not outlined here.
Each additional dot past 1 will give the retainer 20 extra XP to assigned to the character sheet to represent their growth and time spent training.
Specific retainer rules
Animal Ghouls - Use the base statistics in either the Darkages 20 Book or Ghouls 20 Book whichever is higher/preferred. They gain 1 dot in potence plus 1 dot in a discipline chosen by their sire.