You can propagate a yucca plant by taking cuttings from the plant or from offsets at the base of the trunk

From cuttings

Take a cutting: In spring or early summer, use clean, sharp shears to cut a 3-inch or longer piece from a mature part of the plant. 

    Prepare the cutting: Remove all but the top few leaves to reduce moisture loss. 

    Dry out the cutting: Place the cutting in a cool, shady spot for a few days to allow it to dry out. 

    Plant the cutting: Put the cutting in a pot with potting mix or a cacti and succulent mix. You can also add rooting hormone powder to the base of the cutting. 

    Water and place in a warm spot: Water well and place the pot in a warm, sunny spot with indirect light. 

    Wait for roots: After a few weeks, new roots should form and you can repot the cutting. 

    From offsets 

    Cut an offset: When repotting the plant in spring, use a sharp knife to cut off an offset from the base of the trunk.

    Dry out the offset: Allow the wound to dry out for a few days.

    Plant the offset: Put the offset in a new pot with potting mix and water well.

    Place in a warm spot: Keep the pot in a warm spot.

      You can also propagate yuccas from seed.