There have been quite a few debates, trials and comparisons between potatoes that have been chitted and those which have not. Chitting is just allowing the seed potatoes to develop small growing shoots before you plant them in the ground.
The bottom end of the potato is where it was attached to the root of the plant. This is a bit like an umbilical cord.
At the opposite end of the potato are the eyes from where the shoots start to grow - or chit.
Seed potatoes should be unwrapped immediately and set out somewhere frost free and in the light. Do not keep them in the dark or they will develop white, brittle and straggly shoots. I have these in a garden shed next to a window.
I don't know much about Oca, but I assume that as these are tubers that they will need the same chitting treatment.