How do I unlock my iPhone 8

For starters, where did you buy this iPhone? I believe you are referring to the Activation Lock, which is a security measure designed to prevent others from using your device. This is sometimes used on resell devices to take advantage of others. The only way to unlock your iPhone is to contact the original owner, otherwise it cannot be bypassed and is practically a brick. Next time, only buy from trusted sources, so you don't get scammed.

Please read this informative user tip on the risks of buying resale Apple products ⇢

The All Too Common SAD Reality of Buying … - Apple Community

If you are the owner or the owner has shared all information with you then to open Activation Lock:- If it is Activation locked, read here --> Turn off Activation Lock - Apple Support Activation Lock for iPhone, iPad, and iPod touch - Apple Support

Learn how to remove a device from a previous owner's account.

If you are not the owner and do not have the Apple ID and Password then there is no way that you can get into this iPhone unless the original owner shares the Apple ID and password with you. If you are lucky you can get into this iPhone if they (owner) accidentally remove the device from their Apple ID.