* List open source on your resume.
* During interviews talk about your open source accomplishments. Use open source as a way to show you have experience in software development. This is especially helpful with team based open source projects.
* If you are contributing to an open source project with a community be vocal in that space. Answer stack overflow questions, write blog posts, tweet, and get involved in other online areas where discussion takes place.
* Build a website for your open source project. HTML content is easier for most people to consume compared to a github repo with README.md.
* Speak at a conference or meetup. A great way to get started with this is to give a 5 minute lighting talk demo for the project at your local language meetup.
Doing these things will help you market yourself and your open source work. This usually opens the door to networking with people that have similar interests, which is a great way to further your career.
So, you don't have actively leverage it, the companies that value your OS contributions will see it as a big plus point in your resume.
However, what you can do is leverage the power of the OS community to get jobs. This can be very useful when first starting out.
Otherwise, your work really has no context in which it can be judged favorably.
The simple fact that you have OSS on your resume makes you stand out. Period. I have seen exactly one resume with OSS on it in all the years I conducted interviews.
One.
You have to customize the information depending on the company and how likely the group you are applying to cares about open source contribution or connects the dots.
Considering you are contributing to iOS open source project and assuming you are applying to iOS/mobile related opportunities, I will suggest listing your contributions under "Professional Activities" or "Personal iOS/Mobile Activities/Projects'.
In iOS area, you might be better off creating your own side app and listing that on resume than open source contributions.