Commercial Electric 81725 Installation guide

I have reviewed the product details for the Commercial Electric Lamp Nipple 81725. This document specifies that the product contains 8 assorted nipples in 4 different sizes, all with 1/8-IP threads, intended for repairing or custom building light fixtures. I can answer questions about the dimensions, installation, and materials.
What should I do before installation?

What kind of wire does this pipe contain?

What should I pay attention to when filling the pipe with wire?

How to join pipes?