dear open your application manager

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In the Application Manager:

# Navigate to the application menu (tap the title bar)
# Select ‘Application catalogs’
# Select ‘New’
# Enter a catalog name of ‘Maemo extras-devel’
# Enter a web address of http://repository.maemo.org/extras-devel/
# Enter a distribution of ‘fremantle’
# Enter components of ‘free non-free’
# Select ‘Save’


and u can use cssu no any problem