To add a vowel to a consonant, first type the consonant and then the vowel.
Vowels correspond to English letters based on sound transliteration and physical resemblance.
E.g., Hiriq is both i and period (".").
As usual, if the letter is not where you expect, try the upper-case.
Here are some less obvious vowels:
Dagesh/Mapiq is "!". Dagesh strengthens/emphasizes a letter (a soft sound becomes a hard sound).
Mapiq makes ה audible. So it also emphasizes the letter.