To re-thread tent poles, remove the snapped elastic shock cord from the pole sections.
Take the end of the new elastic shock cord and tie a knot in it. With the metal collar of one of the sections facing you thread the opposite end of the shock cord through the section until the knot reaches the end of the tent pole. Repeat this process until you have all the sections of the pole on the shock cord and the pole sections fully connected with each other.
Put a bit of tension on the pole, not overly tight, and then tie another knot in the end of the shock cord and cut off any extra.
Shockcord can be purchased from www.campingspares.co.uk