Enter the "Data\F4SE\Plugins\Translations\ShadowBoostFO4" directory and create a folder with the initials of the language you want to use, the folder name must match the "Fallout4.ini" file under "sLanguage", for example "sLanguage = en" the name of the folder to be create will be "en" without quotes.
Then you have to copy the "Language.txt" file located in the "en" folder and paste it in the folder you have previously created.
Attention the file must remain UTF-8, to be sure to open the language file with programs such as notepad++, to wrap the text write a slash, the program will see it as a carriage return.
Finally, if running the game the language characters do not appear as they should, paste a font file with extension ttf in the translation folder, the font file name must be "font.ttf".

folder structure:

Data\
 |___ F4SE\
         |____ Plugins\
                   |______ Translation\
 |________ShadowBoostFO4\
                     |_________ en\
                     |          |___ Language.txt
                     |          |___ Font.ttf (optional only if needed)
                     |_________ de\
                     |          |___ Language.txt
                     |          |___ Font.ttf (optional only if needed)
                     |_________ fr\
                                |___ Language.txt
                                |___ Font.ttf (optional only if needed)