Hello,
You can find detailed instructions in the accompanying pdf documentation that comes with the bundle download of the plugin.
You can get the bundle download from: https://www.dashed-slug.net/downloads/
Please see under APIs -> Wallets JSON API -> Programmatic access to the Transactions API
You must first assign the access_wallets_api capability to the user.
You can use the plugin’s capabilities section to assign this capability to all user roles except the Administrator (for safety). If you wish to use the API with an administrator account, use any plugin that can edit capabilities to assign access_wallets_api.
with regards