Install on iPhone
Install before you travel, while you have Wi-Fi. The eSIM's days only start counting when it first connects abroad.
Easiest: one tap (iOS 17.4 or newer)
Open your eSIM page (the link in your email) on the iPhone.
Tap Install on iPhone, then follow the steps in Settings.
Or scan the QR code
Open your eSIM page on another screen, like a laptop.
On the iPhone: Settings → Mobile Service (or Cellular) → Add eSIM → Use QR Code.
Scan the code and follow the steps.
After installing
When iPhone asks you to label your plans, choose Travel for the new eSIM (or tap Custom Label and type a name, like "Spain").
Named it something else, like "Secondary"? Settings → Mobile Service (or Cellular) → tap that line → Cellular Plan Label → Travel.
When you land: Settings → Mobile Service → Travel → turn on Data Roaming.
Set Mobile Data to use the Travel line.