Version 1.16.0 required to see and manage reactions in the mobile app
Below are the various ways you can react to an announcement depending on the platform you're on. You're always able to choose the emoji that is being reacted by tapping the + button at the end of the reactions list on an announcement.
iOS/Android Mobile App:
Double tab an announcement card from the dashboard to react with a ❤️ emoji
Tap an existing reaction to place yours for that emoji
From the announcement details screen (tapping an announcement once from the dashboard), there is the reaction bar at the bottom of the screen. Tap any existing reaction or the + button to select a new reaction.