Currently, you cannot register an MT4/MT5 account directly through the Axi Trading app during your initial registration. You must first register an Axi Trading account, after which you can add additional MT4/MT5 accounts. For more details, please refer to this article.
Your login credentials are shared across both the Axi app and the Client Portal. If you signed up via social login (Apple, Facebook, or Google), use that same option to access the Client Portal. If you registered with an Email and Password, those same credentials will provide access to both platforms.