Change plugins language

Hi,
Please i have a little problem, i’ve installed “AccessPress Anonymous post plugin” It’s help me to let users post their own post on the website, but my problem is that the Form is in english and my website is in french, i tried to use ” Loco Translate” to translate the plugin and i found out that there is already a file of french language with the plugin but i don’t know how to use it in the website

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