Patient and Public Involvement and Engagement (PPIE) is recognised by the National Institute for Health and Care Research in the UK as crucial for high-quality outcomes with numerous benefits for patients. Patient and public contributors can provide both personal knowledge and lived experiences which complement the perspectives of the team. In this commentary, we share our experiences of facilitating a project, Explain.Health, to co-design a digital platform to help patients better understand their hospital letters by explaining medical terms. We describe the stages in the formation of the PPIE group, the stages in the co-design process and the next steps for the project. We reflect on PPIE of the project, including lessons learned for future PPIE work in building new digital platforms. Important considerations for this PPIE work include: (1) ensuring each public contributor feels listened to and understands how their involvement contributes to the design of the platform, (2) providing regular and clear communication and (3) offering adequate support to public contributors (appropriate formatting of resources for visually impaired contributors, incentives, assistance to use the meeting platform) to establish an inclusive and considerate approach. These findings can inform future PPIE plans for stakeholders involved in similar projects.