Basically all you need to do is to open Smartwatch application (like Galaxy Wearable) on your phone, follow the steps to pair your phone and smart watch via Bluetooth, when prompted, choose eSIM activation menu
judging from the box its a LTE model so its compatible with a esim. you will need to check if your mobile phone network / carrier supports esims and there maybe additional cost per month or a contract needed. I know for a fact EE does as I had a 46mm LTE on contract with EE myself.