1. Have at least 1 post on Facebook.
  2. Press and hold down on the 'like' bar.
  3. The reactions will show after 0.5 secs. - Keep holding down.
  4. Slide your finger along the 'like' bar to select your reaction. - Keep holding down.

Then once chosen the reaction release your finger and the 'like' status will change to the reaction you have chosen.