Set up Keys

First, we need to get the public key of the person we want to chat with. To do so, we can go on the block explorer and look at the transactions the address has sent. From there, by looking at the raw transaction data, we can find their public key. Once we have their public key, we can use it to encrypt messages that only they can decrypt.

Then we need to set up our wallet to cypher the message and send the tx

import {Wallet} from "xrpl"

const receiverPubKey = "the public key from the explorer here"
const myWallet = Wallet.fromSeed("your seed here")