Instill Energy

Enchant creature
Enchanted creature can attack as though it had haste.
{0}: Untap enchanted creature. Activate only during your turn and only once each turn.

30th Anniversary Edition

Masters Edition IV

Enchant creature
Enchanted creature has haste.
{0}: Untap enchanted creature. Activate this ability only during your turn and only once each turn.

Fifth Edition

Enchanted creature is unaffected by summoning sickness.
o0: Untap enchanted creature. Use this ability only during your turn and only once each turn.

Fourth Edition Foreign Black Border

If attached to an opponent's creature, you can untap their creature during your turn.

Instill Energy's untap ability will not untap the creature until it resolves. This means other spells and abilities can be used before it actually becomes untapped.

Any Auras (or other effects) which are on the creature that would cause it to not be untapped (or have a cost to be untapped) during untap step do not in any way hinder or imply a cost to use this card's ability to untap once during the turn.