How do I remove previous owner iCloud account when they are not available?

Old model iPhone that I was given but I can't find the previous owner to unlock.

How do I remove previous owner iCloud account when they are not available?

You must contact the generous giver (hopefully it is the previous owner).

Each Apple device is linked/associated with an Apple ID of the person who did the setup.

Activation Lock prevents anyone who is not the owner from using this iPhone.

To unlock the Phone, you need the Apple ID and password of the previous owner, that were used during set up.

So you have to contact the previous owner.

The previous owner has to read -> this Apple article: What to do before you sell, give away, or trade in your iPhone, iPad, or iPod touch

What to do before you sell, give away, or trade in your iPhone, iPad, or iPod touch - Apple Support

Then the previous owner has to remove the iPhone from his account, see this Apple article:

Check your Apple ID device list to see where you're signed in

Check your Apple ID device list to see where you're signed in - Apple Support

Then you can sign in with own your Apple ID.

See the following Apple articles:

Activation Lock for iPhone, iPad, and iPod touch

Activation Lock for iPhone, iPad, and iPod touch - Apple Support

How to remove Activation Lock

How to remove Activation Lock – Apple Support (UK)

If you need help removing Activation Lock and have proof of purchase documentation, you can start an Activation Lock support request.

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

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

You can also contact Apple support for help, -> Get Support (apple.com)

You have to show proof of ownership of your product, provide all documentation showing your purchase of the device.

If you do not have additional proof of ownership, contact the reseller. They may be able to provide the original purchase document.

Once Apple receive your proof of ownership, Apple will further review your request and provide an update.

There's no other way, sorry.

Is there any way for me to set this up on my iTunes account..

No. You need the Apple ID credentials for the previous owner to unlock the phone. If you are in touch with the previous owner they can unlock the phone remotely over the internet. See How to remove Activation Lock