How to change plugin translation lunguage?

Hi.

I’m struggling with this issue for hours…

I have installed maillpress plugin.
in the icludes folder there is folder name languages.
in it there is these files: mailpress.pot, MailPress-fr_FR.mo, MailPress-fr_FR.po

I wanted to change some of the values from english to hebrew, so I changed them in the maillpress.pot file like this:
msgid “Loading…”

msgstr “The changed text in hebrew”

I uploaded the file but the text remained in english.

so how do I create a new translation of the plugin and enable it so that the plugin will use a different language file then the default?

Thanks