Seen and Saw

Saw is the past tense form of "see."  Saw can be used by itself, without a helping verb.

You saw me.  I saw that movie.

Seen is the past participle form of "see."  Seen requires a helper verb, such as "have."

I have seen that movie.  A coyote was seen in the park yesterday.

It is never correct to use "seen" without a helper verb.

I seen you. - Incorrect