To install it, download the file then right-click on it an select 'properties'. Go to the permissions tab and make sure 'execute' is turned on. You can now simply double click on the file to install SheetCam.
If that does not work you can simply unzip the file. The data folder in the zip is a tarball containing everything you need to run SheetCam. Execute run-sheetcam to run SheetCam.