There are lots of info out there if you Google this topic, but in general:
-Wipe down with clean, wrung out rag after use. Sand/dirt act like sandpaper on calfskin.
-Once every couple months apply a cream conditioner (Passier lederbalsam or Oakwood, etc.) with a sheepskin mitt. Buff.
-If you ever use soap, use something well made and well-known like Stubben hamanol soap. No glycerine bars or something that says you can leave it on, or that it is soap and conditioner in one step. Just like your skin, if you apply soap, you must quickly remove it with well-rinsed clean rag. Let dry and then lightly condition.
NEVER use oil on calfskin. It will cause the thin calfskin to separate from the leather it has been glued to!