Vinca major, also known as periwinkle, can be propagated from cuttings or by dividing a clump

From cuttings 

  1. Cut a 4–6 in stem from a plant without flowers
  2. Remove the bottom half of the leaves
  3. Place the cutting in water so the area without leaves is submerged
  4. Keep the cutting in a bright location out of direct sunlight
  5. Change the water every few days
  6. Once roots appear, transplant the cutting into moist, well-draining potting mix
  7. Cover the pot with a plastic bag to create a mini greenhouse
  8. Keep the soil moist but not waterlogged

By dividing a clump 

  1. Dig up a clump of the plant
  2. Gently shake off the soil
  3. Divide the clump into a few sections
  4. Replant the divisions in fresh soil, spacing them 8 in apart in small areas or 12–18 in apart in larger areas
  5. Water thoroughly

You can also try dipping the cut end of the stem in rooting hormone to help establish roots faster.