Settings

The settings are under Configuration, then Settings, then Reactions.

Setting	Default	What it does
Tell authors about reactions	Yes	Sends an author a private message the first time each member reacts to their post. Members can still turn it off for themselves.
Reactions shown in a post’s summary	3	How many of a post’s most used reactions are pictured beside its count.
Largest reaction image (KB)	256	The biggest image you can upload for a reaction.