We currently send the following message when asking a user to sign their wallet when authenticating:
Welcome to {{your app name}}. Signing is the only way we can truly know that you are the owner of the wallet you are connecting. Signing is a safe, gas-less transaction that does not in any way give {{your app name}} permission to perform any transactions with your wallet.
Note: We base the default message on the standard SIWE format.
If you would like to update this message and customize it for your users, you simply need to update this message by passing in the prop siweStatement and your custom message: 
<DynamicContextProvider
  settings={{
    environmentId: "XXXXX",
    siweStatement: "Your custom message goes here....",
    ...
  }}
>