Basic plait.
Three strands, one in each hand and one hanging free.
Cross right hand strand over the middle one, the middle one is now your right hand strand.
Cross left hand strand over the middle one, the middle one is now your left hand strand.
Continue, right hand over middle, left hand over middle, until the braid is the length you want.
To get a neat braid you must work under tension, so tie a knot in the end of the three strands before you start and either get someone to hold it for you or jam it into a drawer and push it closed, or use a long pin and pin the knot to something....the couch? I sometimes use a small stick and tie the cords to it, I can hold the stick beneath my toes and pull against it to keep the tension even.
Try looking up scoobies on google, there are masses of clear instructions about for braiding the plastic laces that are applicable to paracord or leather there.
Cheers,
Toddy