As soon as you have published a project you can share it with others.
Click sharing on the left hand side bar.
Check if your project is public or private.
If your project is set as public then anyone can already view it.
You can also copy the URL and share it. Anyone can read it and execute code chunks but they won't be able to modify the project.
If your project is set as private then others can only see it if you copy and send them the sharable link. They will be able to read it and execute code chunks but they won't be able to modify the project.
If you would like someone to collaborate and modify you can invite them to collaborate on your project