This refers to b2evolution version 0.9.0

To add your own smilie to your toolbar, first you need to open up plugins/_smilies.conf.php in your favourite editor.

Copy one of the existing smilies from the $this->smilies = array( and make sure you paste your code before the closing );.

So, your code will end up looking like this.

'texttobereplaced'  => 'my_smilie.gif',

Where texttobereplaced is the text that when typed will be replaced by a smilie, and my_smilie.gif is the name of your new smilie.

Now all you need to do is upload your my_smilie.gif to img/smilies, and upload your changed _smilies.conf.php

To show the smileytoolbar in the backend:

Change the file plugins/toolbars/_smilies.toolbar.php, line 26 (in 0.9.0.11)

var $display = true;