Problem
As I’m pretty new to Xcode development, I was not sure what to do after I’ve added a package via File>Add Package Dependencies.
After running the next build, the error message ‘No such module: …’ arose.
Solution
You have to add the package to the build phases like this:

To get to this view, open your xcodeproj file, click onto the relevant target and then go into Build Phases. Here you can add your package under ‘Link Binary With Libraries’.