Using the command “/help” will bring up ALL the commands for admin.  But if you've recently installed a new plugin and aren't familiar with it, the best place to learn how to use it on the site where you found it.  From there you should be able to find a description/instructions on how to access your plugins using the commands.  Also, check "google" or MCPE forums such as http://forums.pocketmine.net/index.php?plugins/.