How is glycogen made?

Through condensation reactions.

Glycogen is a polysaccharide. This means it is the polymer of many monosaccharides. The monomer of Glycogen is Glucose. Glucose, through condensation reactions in which water is released, joins to form the branched structure of Glycogen. This feature is beneficial in animals as it is easy to break off the individual glucose for energy through enzymes but also because polysaccharides are insoluble while monosaccharides are.