All you have to add here is a simple plain unity UI button into the position pointed by the red arrow.
Create a UI button, and name it whatever you want, as shown below.
Congratulations! You have successfully setup your friends list.
Press play, and click on the friends list button (0 friction), or login and then click the button. If you have any friends, they will to shown to you right away!
In case you have friends, you will see a similar screen like below:
If not, you’ll be presented with a dialogue which tells you that you currently have no friends!