[+1]: Elementals you control get +2/+0 until end of turn.
[−1]: Add {R}{R}.
[−2]: Chandra, Novice Pyromancer deals 2 damage to any target.
Because it’s a loyalty ability, Chandra’s second ability isn’t a mana ability. It can be activated only any time you could cast a sorcery. It uses the stack and can be responded to.
Chandra’s first ability affects only Elementals you control at the time it resolves. Elementals you begin to control later in the turn won’t get +2/+0.