Press:
+
to type a síneadh fada on a lower case vowel
and
+
+
to type a síneadh fada on an a capital letter
Press:
+
to type a síneadh fada on a lowercase vowel
and
+
+
to type a síneadh fada on a capital letter
If the instructions above don’t work for you, you can choose the letter you want in the table below and then copy it (Ctrl+C) and paste it (Ctrl+V) in the right place.
á | é | í | ó | ú |
Á | É | Í | Ó | Ú |
There’s more information available about typing síntí fada here.