sprite.setSpeed

sprite.setSpeed sets Speed on a sprite object. It takes id and fps.

sprite.setSpeed(id, fps)

function start() {  const id = sprite.create('/sprites/hero.png', 100, 120);  sprite.setSpeed(id, 30);}

sprite.create is there to give the call something to act on; sprite.setSpeed is the line that matters. The code sits in start(), which the engine calls once, when the entity spawns.