I bought an iPad second hand and I would like to unlock the activation lock. How would I be able to do this?

Without the Apple ID and Password of the original owner, you will never get past Activation Lock which is a theft prevention feature. As Kirk suggests, if you know that person have them follow instructions in this link...

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

You could ask for your money back or you could recycle the device at any Apple Store.

Here are the Apple support pages that outline the Activation Lock - and the only mechanisms by which it can be turned off:

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

Turn off Activation Lock – Apple Support

As you will discover, unless you are the owner of the AppleID that was last used to activate the device, you’ll not be able to defeat or bypass the Activation Lock. With documentary evidence that you are the original owner (such as sales receipt showing the serial number), Apple may be prepared to assist - otherwise they and nobody here will be able to help you.

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

If you can't get this iPad working for you, and you cannot reach the previous owner iof this iPad OR tge previous has no clue how to unlock it because the seller can't remember the needed information or does know the needed information, return it and get your money back!

This is a dead, useless device to you.

You will never get this iPad to ever work for you.

Sorry & Good Luck to You!

Give it back and ask them to set it up as new.