It is important to note that libraries do not have to use any plugins if they are satisfied with how their system operates. If a library does want to utilise a plugin it is vital that they test it on their staging first to be sure it will not negatively impact the performance of their system. If in doubt, don’t. 

Before any plugins can be added to your system, it is necessary to configure your system to allow plugins to be uploaded.
If plugins enabled on your system when you go to Koha administration, there should be a heading Plugins.
Clicking this link will bring you to a page with an option to Upload plugin.
If all of this appears on your system, you are set up to upload and configure plugins. 
If this does not appear on your system you will need to contact Interleaf Technology to have the plugins enabled.