Plans are packaged in modules and must be installed using Code Manager.
Unlike tasks, PE doesn’t come with any pre-installed plans or modules that contain plans. You must either download modules that contain plans from the Forge or write custom plans.
To install a new module containing a plan, find the module you want on the Forge and follow the r10k or Code Manager install instructions under Start using this module. The modules containing plans have a Plans section in the README.