Pairing my iPhone watch to my iPhone

Your description suggests that the watch has the Activation Lock on. See About Activation Lock on your Apple Watch

If you bought it new return it to the store. If you bought it used, only the previous owner can remove the activation lock. You will need to get in touch with them. The lock can be removed by the previous owner remotely following the instructions at the foot of the linked page:

If you can't access your iPhone or Apple Watch, or if your Apple Watch isn't paired with your iPhone and you need to turn off Activation Lock:

1. On a computer, go to iCloud.com and sign in with your Apple ID. 
2. Go to Find My iPhone.
3. Select All Devices, then click your Apple Watch.
4. Click Erase Apple Watch. Select Next until the device is erased.
5. Click the remove button  next to your Apple Watch.

The person that you bought/got this watch from needs to follow all the steps on this page;

Remove the Activation Lock so that the buyer can use it.

If they can't or won't then get your money back or recycle the watch and mark it down as a bad experience.