Sending money to other Magenta Pay users is very easy through the central button on the home page. Alternatively, you can do it through a chat with another user by tapping the corresponding money icon. You can then enter the exact amount you want to send and confirm the transaction using your device's biometrics.
Alternatively, you can transfer money to another Magenta Pay user through the "Transfer" section in your wallet, where you will be prompted to enter the IBAN and full name of the user you want to send money to.