Hi , i just got this apple watch from someone and its not updated to the latest version so i wanna know how can i update it also its on low battery

Hi

First charge your Apple Watch:

Check your battery and charge your Apple Watch - Apple Support

Then update your iPhone to the latest version of iOS (start by making a backup):

Update the iOS software on your iPhone, iPad, or iPod touch - Apple Support

Then pair your Apple Watch by following the remaining steps here - watchOS will be updated as part of the process:

Set up your Apple Watch - Apple Support

You will need to charge it then pair it to your iPhone in order to update the watch.

Set up your Apple Watch - Apple Support

Erase your iPhone, iPad, iPod touch, or Apple Watch - Apple Support..

Update the software on your Apple Watch - Apple Support