If using the Fastrack version, the connector wires should be included to attach to the terminals under any Fastrack section.
If using the older style with the lock-on (or if wires are missing), use the "aux power" connections and a few convenient lengths of wire. Wires can be connected either to the terminals under any track section (solder them to the terminals or use the proper 0.110 connectors) or to the transformer terminals powering your track via the usual methods.