Currently Crowd does not have a Universal Plugin Manager - a User Interface with the function of managing plugins for Crowd. 

Improvement requests regarding this matter:

• CWD-3237 - Getting issue details... STATUS
• CWD-3157 - Getting issue details... STATUS

Currently, in order to enable a self-developed plugin, you will need to put the .jar into the plugins directory, a sub-directory of your Crowd Home directory. See the documentation: Developing Plugins for Crowd