You will need a copy of the Seedr Kodi add-on and a Seedr account.
Open Kodi, go to System > Settings > Add-ons
Click 'Install from zip file'
Select the zip file you just downloaded, install it, and enable it.
Go to Videos > Add-ons
Click 'Seedr.cc' and copy the device code
Go to seedr.cc/devices, enter the code at 'Add media devices' and click 'Add'
For a tutorial with screenshots on how to run Seedr on your media center with Kodi, go to our Kodi Addon Tutorial.
We do not currently support Plex.