The software should install in whichever language your computer's regional settings are defaulted to, however, if this is not the case, you can change your UI language by going to the Options menu, then General > Application Defaults and selecting the language of your choice.
The available UI languages are English, Portuguese, Spanish, Italian, French, German, and Dutch
From the "User Interface language" dropdown menu, select your chosen language and click "OK".
The application will close and re-open with the selected User Interface language. You do not need to do anything more.
