Reset it here: https://iforgot.apple.com/iForgot/iForgot.html. Once you have your new password, to change it for iCloud on your phone you'll have to go to Settings>iCloud, scroll to the bottom and tap Delete Account. This will delete the account and synced data from your phone but not from iCloud. Then sign back in with your new password and turn your iCloud data syncing back to On, and when prompted, choose Merge.
This site contains user submitted content, comments and opinions and is for informational purposes only.
Apple disclaims any and all liability for the acts, omissions and conduct of any third parties in connection with or related to your use of the site.