[Plugin: Participants Database] switching languages

I noticed the languages folder within participants-database, but I don’t see anywhere in the admin of the plugin (wp backend) to change them.

I see a .po file which I assume is where I need to put the translated bits.

So my questions are:

1- how to change languages in the plugin?
2- do I need only to edit the .po file?
3- is there already a spanish translation, or in case not, can I send it over once its done to be included in the plugin?

Thanks.

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