PM's

There is an icon for it on the top right of the screen:

You need to be friends with someone to be able to send them a message - Zengarden shows the steps for this.

That's for the mobile version 

TheCatWoman uses a desktop computer if I recall correctly, but the steps are much the same for adding friends in order to message them.

Another way to do this on the desktop (or PC) version is to hover the mouse over the users icon/avatar and you will see a Request Friendship option to click on.

Thank you for explaining 

Thank you for explaining