Where do I find the pairing animation on my Apple Watch

Hi

Follow the instructions here to pair and set up your Apple Watch:

Set up your Apple Watch - Apple Support

If the watch has become unpaired according to your iPhone, but has not yet been unpaired according to your watch, you will need to erase it first:

On your watch, go to: Home screen (via a single press on the Digital Crown) > Settings (cog icon) > General > Reset > Erase all Content and Settings.