Where to put language file in plugin folder


Im not sure i totally understand, the different files for translation; .pot, .po, .mo

My situation is that im running multisite with WPML installed for handle translations.
WPML can work for multi site (but not the way i want it to work).
Each single site will have to make translations them self, this means for plugins and themes too.
I want the new sub sites to have plugin and themes translations, from beginning.

I was then thinking about how i can do this, from WPML im able to export a .po file, if i take this file and put in language folder will the translation then be a part of the plugin and just can show up when that language is active? Or how should this be done?

Best regards,