Opening files from BaseCamp is only available for Windows and Web. Go to File – Open and select Basecamp. Connect with your account if you are not already authenticated. There are several ways to open a project from the Basecamp file picker: 

1. Double click on a project; 
2. Select a project and click Open button;
3. Right-click on a project and select Open in contextual menu; 
4. Select a project and click Enter key.