Let's take an example of translating My account -> Points and Rewards page -> My Rewards string.
The string is "MY REWARDS"
Step 1:
Go to Wordpress Dashboard -> WPML -> String Translation
Step 2:
Select wp-loyalty-rules plugin file in "in domain" section and after loading, you can search for the string and click on the search option
Step 3:
Then you can add the translation for respective language (I'm translating the string to "Spanish") by clicking on "+" symbol, add the translation for Spanish and enter
Step 4:
Now, the translated string will get reflected correctly.
Likewise, we can search for the strings from "String Translation Table" of WPML and translate it.