This is the official link to how to acknowledge EU funding:

https://ec.europa.eu/research/participants/docs/h2020-funding-guide/grants/grant-management/acknowledge-funding_en.htm

Use the following text in an acknowledgement section and ensure that the EU emblem (link to loads of accepted versions: https://europa.eu/european-union/about-eu/symbols/flag_en#eu-emblem) is also included next to this text:

Acknowledgement: This project has received funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement No 773521