The quick way - but you have to know the three letter code of your language:
1. See the part "all"
in the URL
2. Replace this by you language, for example "dut"
for Dutch, and you will get
3. From here you can download the subs in your language by episode or by season.
The natural way to get there is:
1. Go to some episode of this tv-series, for example the pilot https://www.opensubtitles.org/en/search/sublanguageid-all/imdbid-1940498
2. In that list, click on the flag of your country/language.
3. Click "All subtitles for this TV Series"
Note that you can set a preferred language in your profile page.
If you do, all search results will include only that language.
Sorry. I am The-King-of-Making-Easy-Stuff-Difficult.
Some very good friend of mine, who prefers to remain anonymous (modesty, I guess), pointed out to me that things are actually quite easy:
Change the search field option to your language and then search, you got those results cos you left it as 'all.'