Calming an IBS flare is normally a mix of diet and lifestyle actions. It can take a few days, or a few hours, but some of the things I recommend include
gentle movement like walking, to shift trapped gas
Wearing a loose fitting waistband because tight clothes can make cramps and pain worse
warmth such as a hot water bottle or a warm bath to sooth
eating a lower FODMAP diet for a few days to remove fermentable carbs
going easy on yourself, take time to recover
You can read more about how to calm an IBS flare in my blog post.