Translation:أَهْلاً يا رَواد.
I am a native speaker so I know what I am saying...
it's not wrong to forget to say it, but it's kind of important in the sentence but the sentence is not wrong without it, and actually, every native speaker always says it, but foreign people forget sometimes.
plus: sometimes it changes the meaning of the sentence.
Remember to go through the Tips and Notes of this skill (on the website, won't be available for Arabic on the app), its explained there.
In short, it is a respectful (yet can be informal) and a common way to address people before mentioning their name. It can be said to grabs the person's attention.
You can directly translate "ya" as "O" in English - "O Lord, bless...." or something similar.