I was given a second hand iphone. How do I login with my Apple ID without knowing the old ID account

You cannot use until you can sign out with the original account Apple ID & password.

You don't. The phone is protected by the theft deterrent feature Activation Lock. The only way the phone can be made usable is if the person who set it up unlocks it. See: Find My iPhone Activation Lock: Removing a device from a previous owner’s account

You don't. Talk to whoever gave it to you. They will have to remove the activation lock, assuming it's locked with their account.