Find spider webs in abandoned mineshafts, woodland mansions, or stronghold libraries
Use shears to collect spider webs as cobweb blocks
Use a sword to break cobwebs and collect string
Place cobweb blocks where you want the web effect
Use string in a crafting recipe to make tripwire, not spider webs
Use commands in Creative mode to place cobwebs directly
Use `/give @p cobweb` in Java Edition
Use `/give @p minecraft:cobweb` in Bedrock Edition