Separate collard greens into leaves. Trim and discard tough stalk from center of leaves; stack leaves, and roll up, starting at 1 long side. Cut into 1/4-inch-thick slices; rinse under cold running water. Drain well. Stir-fry collard greens in hot vegetable oil in a large Dutch oven over medium-high heat 2 minutes or until greens begin to wilt. Add chicken broth, salt, vinegar, and dried crushed red pepper; stir-fry 3 minutes or until greens are crisp-tender. Gently stir in apples; cook, stirring often, 2 minutes.