If you are installing from a CD, then insert the CD into the drive, and when it becomes visible on your desktop, double-click on its icon. A Finder window appears, showing the contents of the CD. Double click on the Sybase_ASE_1251 package, and the installer starts.
If you intend to install in a headless system, you must make this package visible to that system. You can use the Finder to copy the package to a location that is visible to the headless system (NFS-mounted file system), and then review the section titled Installing on Xserve.