New plants will form at the nodes, the juncture of the stem and leaves. I cut large Hoyas like this into sections, each containing a set of leaf nodes. Leave a little tail of stem on either side of the node to anchor the cutting into the potting medium. Make sure the nodes are under the soil.
I would cut your stem into 4 pieces.
Lin's potting soil is good. Give them lots of water - it may take months but they will root.
