You control a creature that can tap to produce at least ({2} magic symbol) .
Yenna does not have summoning sickness.
Steps
Activate the mana-producing creature by tapping it, adding at least ({2} magic symbol) .
Activate Yenna by paying ({2} magic symbol) and tapping it, creating a token copy of Second Wind attached to the mana-producing creature, then untapping Yenna and causing you to scry 2.
Activate the Second Wind token's second ability by tapping it, untapping the mana-producing creature.
Activate Phantatog's first ability by sacrificing the Second Wind token, causing Phantatog to get +1/+1 until end of turn.