"I can write about and present my research impactfully to a range of audiences."
In a research context, impact can be defined as success in persuading others to change what they do or think. As a researcher, it is your responsibility to persuade relevant audiences that your findings are important, and to explain clearly what you want those audiences to do differently. This could be fellow specialists, researchers in other fields, policy-makers, funding bodies, commercial organisations, and so on.
Good writing skills are essential to publishing papers, crafting funding proposals and engaging with the public conversation around research, while good presenting skills are vital to attending conferences, promoting (your) research publicly and being successful in meetings and interviews.
You can develop these skills through courses run by the University Library and the Public Engagement Team, as well as courses run by Researcher Development. The Language Centre also has an excellent set of online resources on Academic Writing, aimed at international students but often also relevant to native English speakers.