A Paper addon must be compatible with your versions of Minecraft, Java and server software. Read the dependencies on the distribution page before installing the file.
Step by step
-
Download the jar file published by the official project or developer. Using random repackaged files of the same name.
-
Shut down the server properly. Put the plugin jar in the
pluginsdirectory and add the necessary dependencies with their compatible versions. -
Start the server and check the plugin loading line. Keep a default copy of the first boot configuration before editing it.
-
Test a feature of the add-on that is available to the regular player. Just because it appears loaded in the console does not indicate that the configuration is correct.
Keep in mind
Renaming a zip file to jar. Look at which file will be installed within the release.