how to add custom menu in admin side

See http://www.chipbennett.net/2011/02/17/incorporating-the-settings-api-in-wordpress-themes/

If this is a theme options page, then it should be listed on the Appearances menu.

If it is a theme options subpage you should use add_theme_page() to add the submenu.

If you want to have general control of the adminpanel menues you can use the plugin admin_menu_editor by Janis Elsts