In order to receive Bitcoin from any address, you should provide your public address to the sender. To do so, you need to tap the “Receive” button. There you will see a QR code which you can show to the sender if they have a QR scanner. Otherwise you can copy the address by tapping on it.
You also can tap “Share” to send your public address via other applications such as “Mail”, “WhatsApp”, and others. You also can specify the exact amount that you want to receive by clicking “Add Amount” but it works only with a QR scanner.