Locating the tools
Those tools are SOPs.
After creating a geometry node in the obj context, you will find them in the tab menu's Digital Assets category.
Generating the yarns
You'll have to specify a reference frame to initialize the yarns. They will then follow the input object surface deformation while growing if you enable it.
The tools can output curves or geometry.
While in curve mode, you can enable shaded yarns display by ticking "Shade Open Curves In Viewport" in the Geo's "Misc" tab.
In case of deforming geometry, please choose the ref. frame carefully, with as less face overlaps as possible.
This will save you from some disappointments.
Those tools rely heavily on the quality of the objects you use as an input.
For good results they should have:
Suitable vertex UVs (a.k.a clothing patron style, low distorted and overlap free UVs)
While in curve mode, you can choose to switch from growing to carving animation by appending the Jop CarveTool.
The yarns will be cutted instead of growing along the surface, canceling texture sliding effect inherent to growing animation.
The choice of the animation type is purely aesthetic.
With the Jop StandTool you'll be able to convert yarn to multi-strand.
Again, the upstream tool has to be in curve mode otherwise an error message will pop up.
As this tool may produce a huge amount of curves, it is intented by design to be rendered as hair primitives, so no meshing option is provided. Nevertheless, it carries a consistent "transform" attribute to guarantee proper mesh orientation if you decide to mesh it later on using a Sweep node.