The primary race is the race selected in the race field. After that you can select another race as a great blood talent, for 10DP, to create a hybrid of two races, like an Half-Elf (Human/Elf hybrid), or you can select up to two lesser blood talents, for 5 DP each, to create a mixed heritage of up to three races, like Human/Elf/Dwarf.
My hybrid test character Human/Elf/Dwarf has this for background: his maternal grand-mother was an Elf and his paternal grand-father was a Dwarf. So he inherits some aspects of the other two races while being primarily Human.
The second hybrid character is a mix of Halfling and Dwarf. This character's father was a Dwarf, making the Halfling a Half-Dwarf. He is heavily influenced by his father so he was many physical aspects of a Dwarf, as well as several talents. He is primarily a Halfling, while looking a lot like a Dwarf.
Both case cost 10DP, but create vastly different characters.
Chapter 13 Encounters and Monsters has all the necessary information to add several monsters as character races. I would them out of the basic database to let GMs decide if they want them or not. I'll add those races in, I'll be able to create NPCs of those races through autoHarp.