On iOS, open Safari and go to your wallet address https://victoriassecret.smartmediawallet.app/. From there, tap the Add icon at the bottom of the screen (the little box with the arrow pointing up), and tap Add to Home Screen. Next, type in the name you want to use for the shortcut, and the wallet icon should appear on your home screen.
On Android, open Chrome and go to your wallet address https://victoriassecret.smartmediawallet.app/. From there, tap the three dots in the top right corner and tap Add to Home Screen from the list. Tap Add automatically and the link should appear on your home screen.