It's a phrase used to emphasize that you were right about something, often with a touch of smugness.
Breakdown:
* YA: This is short for "You," but used in a less formal and more emphatic way.
* govoryu: This is the verb "to speak" in the past tense.
* na: This is a particle that emphasizes the speaker's certainty.
So, the whole phrase translates to "I told you, didn't I?" or "See, I was right."