Rule 122.6 · Counters
Some spells and abilities refer to counters being put on an object. This refers to putting counters on that object while it’s on the battlefield and also to an object that’s given counters as it enters the battlefield.
Subrules
If an object enters the battlefield with counters on it, the effect causing the object to be given counters may specify which player puts those counters on it. If the effect doesn’t specify a player, the object’s controller puts those counters on it.