You don't give enough information to enable a detailed answer. Have you forgotten your password? Go to http://iforgot.apple.com and sign in with your iCloud login. A new password will be sent to your associated email address. If this doesn't work you will have to contact Support. Go to https://getsupport.apple.com . Click' See all products and services', then 'More', then 'Apple ID', then 'Other Apple ID Topics' then 'Lost or forgotten Apple ID password'. If you have any problems with that try this form: https://www.apple.com/emea/support/itunes/contact.html