1- Download Cocoon plugin for Grasshopper from Bespoke Geometry.
2- Unzip the folder and make sure that the Grasshopper file is unblocked (right-click on it and unblock it).
3- Copy the files to the "special folders -> component folder" of Grasshopper.
4- Restart Rhino/Grasshopper after installation is complete.
Watch this youtube video tutorial on using cocoon.