Add this under main:
gMissionRunning = true
while gMissionRunning do
if IsButtonPressed(0, 0) --This is the left arrow on the keyboard
PedSetActionTree(gPlayer, "/Global/Player", "Act/Anim/Player.act")
elseif IsButtonPressed(1, 0) -- Right arrow on the keyboard
PedSetActionTree(gPlayer, "/Global/BoxingPlayer", "Act/Anim/BoxingPlayer.act")
Wait(0)
end