Lots of things missing from everyone telling how to mitigate this: 1) how do I check what version of log4j I am using? 2) how do I upgrade my log4j version 2

Lots of things missing from everyone telling how to mitigate this: 1) how do I check what version of log4j I am using? 2) how do I upgrade my log4j version 2 to the latest? I download the new zip, then what?