Those are just ";tuplets."; In this case, 5 notes are to be played in the space of 3, so a ";ratio"; tuplet was used. In Sibelius, this was simply entered using the Create>Tuplet command, and using 5:3 as the ratio.
You can create those notes by clicking the measure or notes that you want to create some text above, and hitting (Control + T in Windows, maybe Command +T on a Mac).
You can type in your specified numbers, and the trick to getting the single note values is a [b]right click[/b] in Windows and the equivalent ";Control + click"; on a Mac. A large menu will appear with several special text choices you can insert above your music, including many note values. ***Note: you right click while you are still in a ";text editing"; mode. So, sequentially: Ctrl+T, then a right click to access said menu.
(if a Mac person wants to confirm/correct those shortcuts...I'm not a Mac user).