Craft it in a Fabricator
Unlock the Polymer engram
Gather resources: Cementing Paste and Obsidian
Use Organic Polymer as a substitute in some recipes
Harvest Organic Polymer from Kairuku, Mantis, Hesperornis, and other sources
Buy or trade for Polymer on servers that support trading
Loot Polymer from supply drops, caves, or boss rewards if available on your map
Check the specific Ark map for its available Polymer sources