Angel Watch™ is fully unlocked and will work on just about all global networks (4G/GSM/LTE).
Wherever you are, you can select any plan that has voice and data, around 1000 minutes (~17hrs) and 1GB. This is usually plenty.
You will also just have to make sure to update your watch's APN setting to the Android setting of your network provider. You can search online for: "what are (your provider) android APN settings" and you'll be able to select the correct APN setting on the watch and connect to the 4G data you'll need.
For customer in the USA wishing to use their own GSM (not CDMA) network, this may come with varying degrees of complexity.
For example, if you choose to instead be on AT&T directly, it will be required to activate the SIM in a regular Apple or Android phone first using that device's IMEI. After confirming that the SIM is successfully activated by checking calls and internet browsing in that phone (with WiFi disabled), you may remove it and insert it to your Angel Watch.
You'll need to check your networks APN settings for 4G Android devices and make sure this is selected/entered into the watch's APN settings (Settings-Mobile Networks-APN). In the case of AT&T, this would be NXTGENPHONE, T-Mobile would be fast.t-mobile.com and others are available with an online search.