About the C#m7 chord
To play C# minor 7th, use the first shape above. Place your index finger on the 1st fret of the G string, your middle finger on the 1st fret of the C string, and your ring finger on the 2nd fret of the A string. Leave the E string open. Strum all four strings and check that each one rings cleanly.
Root
C#
Quality
Minor 7th
Notes
C# · E · G# · B
How the C#m7 chord works
C#
Root(1)
The home note. It gives the chord its name.
E
Minor third(♭3)
The defining minor interval above the root.
G#
Perfect fifth(5)
Adds strength and stability.
B
Minor seventh(♭7)
Adds the defining minor-seventh color.