you are in the right place…
so lets stick with core for now… click on simple press core to get the core translations… then you click on the main version you are using, currently 5.2… then go to front end… and there you have all the translations for the front end… find the language you want and click on it… when you get to the language, at the bottom you can export the translation… get the .mo one…
similarly for plugins… back to your main screen… click on plugins… lets pick subscriptions.. click on that plugin… version 1.2… and now again, pick your language and then download the .mo file…
you would do this for each plugin you are using… and then for the theme you are running…
yeah, that glotpress is not the most user friendly piece of software… its the standard wp translation program created and used by WordPress for all of its translations… we just use it too… we will try to clean up the help a bit more and see if we can make it bit more descriptive…