The open beta test will only last for a few weeks as IDC Games plans to launch sometime later this year. (The company is offering a vague Q3-Q4 2018 release date.) When the game does launch, it will offer localization in seven different languages: English, French, German, Spanish, Turkish, Italian, and Polish.
To participate in the beta, head to the IDC Games site and register now. (A bit of a PSA: While the press release does state the beta is available via Steam today, the page doesn’t seem to be up at the moment. So for the moment, the main site may be your only option for now.)