To build a Dminor chord use D,F and A (every other note starting from D) of the Cmajor scale. These three notes are called the root, the minor3d, and the 5th of the chord. Minor is often notated as a dash (minus sign) as in D-.
Build a D- chord. Roll over the notes for hints. Click on the root (D), the 3d (F) and the 5th (A).