There's nothing to tell. All you've got to do is let her know.
5 seconds sound clip from the Swiss Miss (1938) movie soundboard.
You can hear this line at 00:53:17 in the DVD version of the movie.
Quote context
[...]
- Do you mind if I tell you something else? She's in love with you, too.
- There's nothing to tell. All you've got to do is let her know.
- But you don't understand. This is my first love affair and I don't know how.
- Say, why don't you do like the Gay Caviars used to do in the olden days?
- Gay Caviars! What did they do?
- But suppose she's in love with someone else?
[...]