Opening XPS files on a non-Microsoft operating system can prove difficult, as they're designed to be opened with Internet Explorer. The easiest way to circumvent this problem (short of using Windows) is to download a third party program called "NiXPS." The program will allow you to view XPS files for free, although there are other versions you can pay for that will allow you to alter XPS files in various ways.
Open a web browser.
Navigate to the NiXPS website and download one of the offered applications. All the versions will open XPS files, but "NiXPS View" version is free to download.
Install NiXPS by dragging the downloaded file to your "Applications" folder. Now you can open any XPS files you have.