How do I react to an instant message I've received in Skype?

To react to an instant message:

You can easily react to a message by clicking or tapping someone else's reaction to use the same one.

To choose your own reaction:

1. Select the  smiley face button next to a message you've received. A selection of available reactions will display.
   
   Note: New reactions will be added frequently and may differ by region. You can also customize your reaction picker.
2. Swipe left or right on mobile or click the arrows on desktop to choose from additional reactions. 
3. Selecting the emoticon will send it automatically.
   
   Note: On mobile, you can quickly like a message by double-tapping it.

To customize your message reaction picker:

1. Select the smiley face button next to the message you want to react to.
2. Select the Customize Reactions button.
3. Select the minus button next to any reactions you want to remove from your reaction picker.
4. Select the plus button next to any reactions you want to add to your reaction picker.
   • You can have up to sixty reactions in the reaction picker. New reactions will be added to the front of your reaction picker.
   • You can select more emoticons from the various categories at the bottom of the Customize your reactions window.
5. Select Done to save your customized reaction picker.

You can also add custom reactions using chat commands.