Leads are items that can be attached to mobs to pull them along wherever you travel. In the base game, you can attach a lead that is already connected to an animal to a fence post. With this add-on, you can place a leash knot on a fence, allowing you to attach the other end of the lead to another fence.
How does it work?
The leash knot can be crafted simply by putting one lead into the crafting grid. It can also be found in the "Construction" tab of the creative inventory. You can only place the leash knot on the tops of fences. Once it is placed, you will be able to attach a lead to the knot and interact with another fence to attach the other end to it. Minecarts can now be leashed as well. This is very useful for if you want to take a chest minecart with you on your journey. All minecart variants are leadable, but from a smaller distance than a typical Minecraft mob.
Once the pack is downloaded, click on the file and it will automatically import into Minecraft.
If you are on iOS:
Open the file with the Notes app, then from there you will be able to select "Open in Minecraft."