To edit the AJAX panels (not the content in their states) from your site, follow the next steps:
Go to the master page if you are not there (but editing a certain panel state). You can do this in three ways:
Click the Go to Master Page icon in the MX AJAX Toolbox tab of the Insert bar:
Choose the AJAX Panels -> Go to Master Page option in the right-click contextual menu:
Select the Master page item in the AJAX Panels window/floater:
Notice in the Server Behaviors tab of the Application panel the existing AJAX Panel server behaviors, one for each panel.
Double-click the one you want to edit.
The only thing that you cannot change is the panel name (the text box is disabled).
You can also edit some of the panel's properties by using the property inspector:
The property inspector shows when you select the panel in the master page, either by clicking the associated server behavior in the Server Behaviors tab of the Application panel or by clicking on top of the panel, in Design view.