This depends on your Operating System.
For Windows :
Intonation mark
Key combination
Vowels
Tonos/Acute ΄
Dead key (;) + vowel
ά έ ή ί ύ ό ώ (all)
Dialytika ¨
Dead key (:) + vowel
ϊ ϋ
Dialytika with Tonos
Dead key (`) + vowel
ΐ ΰ
For Linux :
Dead key (:) + Dead key (;) + vowel
To use the above combinations, you may need to enable the Greek keyboard layout for your Operating System first.A Dead key is a special kind of a modifier key on a computer keyboard that is typically used to attach a specific diacritic to a base letter. The dead key does not generate a (complete) character by itself but modifies the character generated by the key struck immediately after. (source: http://en.wikipedia.org/wiki/Dead_key )AltGr is a modifier key found on some computer keyboards and is primarily used to type characters that are unusual for the locale of the keyboard layout, such as currency symbols and accented letters. On a typical, IBM-compatible PC keyboard, the AltGr key, when present, takes the place of the right-hand Alt key. (source: http://en.wikipedia.org/wiki/AltGr_key )
Here is more information for Greek Polytonic keyboard combinations and Greek keyboard installation instructions for different Operating Systems:
for Windows:http://www.ellopos.net/elpenor/greek-texts/gr-pol-keys/greek-keyboard.asphttp://www.dramata.com/Ancient%20polytonic%20Greek%20in%20Windows.pdffor Linux: https://docs.google.com/document/pub?id=1oiK5KraVvob6fAEhcVjwI99RlWtnBLiSGgDFs96qrbk
Άνω τελεία και άλλοι «δύσκολοι» χαρακτήρες σε Linux
for Macintosh OS:http://www.dramata.com/Ancient%20polytonic%20Greek%20on%20Macintosh.pdfhttps://apps.carleton.edu/its/flt/assets/GRKpolytonic_Mac.pdf
--------------------------------------------------------------------------------------------------------------------------- Vasiliki Baskou, Instructor/Director, https://learn-greek-online.com.