According to https://neo4j-contrib.github.io/neo4j-apoc-procedures/, one only needs to download the binary jar from http://github.com/neo4j-contrib/neo4j-apoc-procedures/re
If you installed neo4j using a Windows or Mac installer (which most people do), and not from a zip or tar file, then the plugins folder should be in your database folder, not in your neo4j installation folder.
Here is a related answer with a little more detail: https://stackoverflow.com/a/42357481/974731.