Hi khanka, welcome to the forum!
1) It's recommended that Mac users select the AU version of Kontakt Player.
2) Good, the "Virtual Drumline 2.5" sound set is showing up, which means that Sibelius can see that the library is installed.
3) I'm fairly certain that you don't have the sound set at "/Users/yourusername/Library/Application Support/Avid/Sibelius/Sounds" - unless of course that is what your username actually is. Please attach a screen shot showing the entire folder/directory structure pointing to the file.
1) It's recommended that Mac users select the AU version of Kontakt Player.
2) Good, the "Virtual Drumline 2.5" sound set is showing up, which means that Sibelius can see that the library is installed.
3) I'm fairly certain that you don't have the sound set at "/Users/yourusername/Library/Application Support/Avid/Sibelius/Sounds" - unless of course that is what your username actually is. Please attach a screen shot showing the entire folder/directory structure pointing to the file.