There are two ways to express yourself using emoticons in Couple. You can use the special emoji keyboard or a small number of shortcuts that automatically turn into emoticons. Each way is shown below:
You can use the built-in emoji keyboard, which gives you many more choices. Follow the instructions on this page to set it up: https://support.apple.com/kb/HT4976
If you experience problems trying to set up emoji, this article covers the major reasons why it isn't working: https://support.apple.com/kb/ts2450
Note: For those who are using iOS 4.3 or earlier and not on Japanese iPhone devices, the emoji keyboard is unavailable.
You may perfer to use shortcuts instead, or you can't access the emoji keyboard. Never fear - there is a way to use emoticons/emoji regardless.
These are the currently supported shortcuts on Couple: