Hi James, welcome to the SonarSource Community!
You might have missed the section where it’s covered in our docs.
The key part there which answers your question is the bind mount
-v "${YOUR_REPO}:/usr/src"
Where the directory containing your project should be substituted for the ${YOUR_REPO} part. If a sonar-project.properties is included in the root of the project, it will then be picked up.