First clean the scissors you might be using.
Keep the scissors under hot water and clean them well. This prevents you from unnecessarily transferring bacteria during the propagation.
Do you happen to have disinfectant or pure alcohol? Disinfect the tools after using hot water. Let's get away with those bacteria and fungi!
As soon as the scissors are clean you can start propagating. Cut a stem that is at least 10 cm.
A Muehlenbeckia grows best when it's propagated in water. Place the stems in a glass with water, and make sure that no leaves touch the water.
It's important to remove the leaves at the bottom of the cutting. If leaves are hanging in the water the cutting can rot.
After a few weeks you can see that roots are developing on the stem.
As soon as the roots are at least 5 cm, you can repot the cuttings. Place the sides of the roots in the soil. The cuttings may have to get used to the soil a bit, but after a while the cutting will soon make new leaves.