How do I take the activation lock off of this device?

If you can get a hold of the previous owner, provide them with this article so that they can remove the activation lock from this phone: What to do before you sell, give away, or trade in your iPhone, iPad, or iPod Touch - Apple Support

Talk to the person you got it from. If they can't or won't remove the lock, return it and get your money back. If you can't do that, turn it over to the police as it's most likely stolen.

There is no way to bypass the activation lock.

It is an anti-theft feature. It's doing exactly what it's designed to do.

You don’t. If the previous owner can not, or will not remove the lock, the phone is useless to you. Activation lock can not be bypassed.