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To use the Alta Open app on your Apple Watch, first, make sure you have the app installed and configured on your iPhone before proceeding. See How do I log into the Alta Open App?
To enable the Alta Access Open Watch app:
On your Apple Watch, go to the App Store, search for “Alta Open” and download the app.
Or, on your iPhone, go to the Watch app, scroll down to the Alta Open app, and if it’s not already installed, tap INSTALL.
For more information, see Apple's support article.
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