How can I upgrade my units with the Ikanda
Units built in a city with an Ikanda get a special upgrade (Buffalo Horns) when they are produced.
Due to the way upgrades work in Civ V, having the Buffalo Horns upgrade is what lets you later take the Buffalo Chest and Buffalo Loins upgrades.
So to acquire all 3 upgrades, you simply need to train one of your units up to level 3.