These instructions apply to Minecraft on all platforms.
How Do You Make a Lead in Minecraft?
you could collect them by defeating Slimes, which spawn in swamps or underground caves.

Find them in treasure chests or craft String from Cobwebs.
it’s possible for you to find Cobwebs in mines or get them by defeating Spiders.
To make a Crafting Table, use4 Wood Planksof any pop in.

How Do You Use a Lead in Minecraft?
Equip your Lead and use it on a passive mob (like a horse, axolotl, etc.)
to attach it as a leash.

To unleash it, interact with the mob using the controls above.
To set it free, interact with the leash tied to the fence post.
However, a Lead gives you more control over where your animal companions go.

What Do you gotta Make a Lead in Minecraft?
FAQ
To craft a Lead, you need a Slimeball.
To use a Lead with a cow, hit the animal with the Lead equipped.

It will then follow you around.
The mob will then stay within five squares of the one you attached the Lead to.