Swing rhythm occurs when eighth notes are interpreted unevenly as a pattern of long-short durations (subdividing the quarter note into 3’s).  Learn by practicing the count as:

Listen to the opening measures of G Minor Blues first played with straight eighths (counted: 1– &, 2– &, 3– &, 4– &) and then swing eighths (counted 1– &- a, 2– &- a, 3– &- a, 4– &- a):