Cway Quick Share is used for sharing files with no affiliation to a specific project.
When files are shared to you, you'll receive an email with a link to Cway saying that files are available for your download.
Simply select the files and choose Download, either by right-click or in the menu bar. In Quick Share you can make a multiple selection.
In the dialogue that appears you can also choose between files, eg if the shared bundle contains more files than you need.
When you've downloaded the files, the red dot marking the share in Quick Share turns green.