Go to the menu > Add Subtitle File... and select your downloaded .srt file.
If you are watching the series on a platform that does not natively offer English subs, you can use external subtitle files (.srt): Paco's Men (TV Series 2005–2021) - IMDb los hombres de paco english subtitles
Despite its iconic status in Spain and Latin America, Los Hombres de Paco never secured a major international streaming deal with full subtitle support. Here is the current landscape: Go to the menu > Add Subtitle File