Log in to the Azure Portal and Search for Azure Network Watcher and then click on the search result Network Watcher.

Click on the + Add button on the Network Watcher page.

On the Add network watcher window, select the subscription that you want to use here and select the region for which you want to add the network watcher, Finally, click on the Add button.

It will take a few seconds then you will see a message like below that the Deployment succeeded.

You can able to see the Network Watcher got created successfully. Click on the name to see the details of the Network Watcher.