How do I take off my activation lock on my other iPhone

Activation lock is a security protocol that can't be bypassed. Only the person it is locked to can unlock it.

If you bought this from someone and it came locked, try to get your money back, you will never be able to use the phone.

If your phone is Activation Locked - How to remove Activation Lock -

How to remove Activation Lock - Apple Support

The All Too Common SAD Reality of Buying a used phone -

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

Assuming you didn't purchase a used iPhone, which came Activation Locked (which you cannot remove yourself, nor will Apple help you) and you do know your Apple ID and Password, see what to do in this link --> How to remove Activation Lock - Apple Support

If you bought a used iPhone, ONLY the owner who locked the phone can remove activation lock. If you don't know them or can't reach them, the phone is useless to you and can never be used.

If you bought a used iPhone, read this --> The All Too Common SAD Reality of Buying … - Apple Community

Follow the instructions in the Apple Support document above your name. You will need to know the Apple ID and Password that was used to originally set up the phone.

Otherwise, the phone is useless.

Read and follow the article linked above.

Remove from activation lock for my iPhone