My iCloud is locked how can I unlock it

Have you forgotten your Apple ID?, check your Apple ID via your email box, see this Apple article: If you forgot your Apple ID

https://support.apple.com/en-us/HT201354                  

OR see -> Having trouble signing in?

https://iforgot.apple.com/password/verify/appleid

See also this Apple article: If your Apple ID is locked or disabled

https://support.apple.com/en-ca/HT204106