On the DLS and elsewhere, are multiple variations not only based on the country of origin, but also how they're implemented in Trainz. Some are the easy drag and pull to cover the mainline while others are made up of individual components such as insulators, line tensioners , circuit breakers, section breaks, and everything in between. With the component system, these parts are track-objects and scenery objects that are snapped together to produce the catenary. This system looks really, really nice, but it's complicated and time-consuming to setup.
Since this is your first time at this, I highly recommend seeking out the all inclusive spline of wires. Some of these are wires only and you place your poles, which are either a track-object, or are a scenery object, while others include the attached poles as well. In many cases, you'll have to use a combination of these systems in order to achieve what you want.
There are a few more things that need mentioning here. The wire systems in any case are splines and are put down like a road or fence except over the tracks, which means you'll end up with a gazillion spline points not only for the various segments of the catenary wire splines in addition to any track you have as well.
This system is installed secondary to the tracks as you are probably aware. This means that should you need to adjust tracks for any reason, the splines will have to be realigned afterwards once the track adjustments have been made.