From Bitstamp

How to send XRP from Bitstamp to Xaman (deposit)

• Open your Xaman app, and tap and hold your account address (r…) and Copy your account address

• Switch to the Bitstamp app, select Wallet

• Tap the XRP wallet

• Enter an amount to send to Xaman

⚠️ Please note: if your XRP Ledger account (managed with Xaman) has not been activated, send at least 11 XRP (10 XRP reserve and 1 XRP extra in case there are withdrawal fees

• Paste your XRP Ledger account (managed with XUMM) address copied in the first step in the XRP withdrawal address field. Don’t enter a Destination tag, this is not required for XRP Ledger accounts managed with Xaman.

• Confirm by tapping the Withdraw button

• Optionally, if requested: enter your 2FA code and confirm your withdrawal with the e-mail Bitstamp may send you

• Your XRP will arrive in your XRP Ledger account managed with Xaman shortly. 🎉

While this video does not specifically show how to send XRP to your XRPL account managed by Xaman, it does should how to send XRP in general.