You need to place translation files of the theme into the /wp-content/languages/themes/ folder with correct names (language name and xstore theme suffix, e.g xstore-pt_BR.po, xstore-pt_BR.mo).
Then click on button Sync (Loco Translate plugin http://prntscr.com/glemdq) – synchronize your translation file with pot file > you will be able to translate untranslated strings.
Fixed, I’ve sunchronized translation. http://prntscr.com/o7cjnm
1) Do not change the text domain in style.css of the theme, because you will need to change it in all files of the theme.
2) Translation files should be placed in /wp-content/languages/themes/ folder with names xstore-pt_BR.po and xstore-pt_BR.mo, according to text domain.
3) Do not forget to sync translation after every theme update.
4) Do not forget about translation for XStore Core plugin.