My phone is locked in iCloud, I want to open it

If the phone is Activation Locked ("Locked to Owner"), you must supply the Apple ID and Apple ID password that it is asking for. Either to log into the phone itself, or to log in on the Web.

There is no magic bypass to get you past the Activation Lock.

How to remove Activation Lock - Apple Support

If you are the original purchaser of the phone, and have proof of purchase that is satisfactory to Apple (e.g., from Apple or an Apple Authorized Reseller, clearly showing your name and the phone's serial number), you could start an Activation Lock support request. It is completely up to Apple whether to grant such a request – and there is no point in even submitting one if you lack the necessary proof of purchase, or this is a phone you got second-hand.

If this is a second-hand iPhone, see:

The All Too Common SAD Reality of Buying a Used iPad/iPhone – Apple Community