The comma should be placed inside the quotation marks.

Both the beginning and the end of the quotation (from the film Casablanca) should be marked with quotation marks.

Follow conventions when using quotation marks with commas (46h), semicolons (47d), question marks (48b), and other punctuation (50e). Always use quotation marks in pairs, and follow the guidelines of your documentation style for block quotations and poetry (50a). Use quotation marks to mark titles of short works (50b), but use italics for titles of long works (54a).