Create the imageslider.xml file in app/design/adminhtml/default/default/layout/
[php]
<?xml version="1.0"?>
<layout version="1.0.0">
<imageslider_adminhtml_imageslider_index>
<reference name="content">
<block type="imageslider/adminhtml_imageslider" name="imageslider" />
</reference>
</imageslider_adminhtml_imageslider_index>
</layout>
[/php]
[php]
<?xml version="1.0"?>
<layout version="1.0.0">
<imageslider_adminhtml_imageslider_index>
<reference name="content">
<block type="imageslider/adminhtml_imageslider" name="imageslider" />
</reference>
</imageslider_adminhtml_imageslider_index>
</layout>
[/php]
Note:- 1) imageslider_adminhtml_imageslider_index element represent the ModuleName_adminhtml_ControllerName_FunctionName
2) reference element which has name attribute and value is content.
in this block type imageslider/adminhtml_imageslider represents Modulename/adminhtml_BlockfileName.