How to connect a standalone database with PowerApps ?

With On-premises data gateway, Keep your data in Power BI, PowerApps, Logic Apps, and Power Automate up to date using the on-premises data gateway OnPrem Data Gateway - https://www.microsoft.com/en-us/download/details.aspx?id=53127&msockid=1ffae2ad89b3660e2d02f108880167e0