If you're outside India, your options may vary. Here are several approaches to access the film with English subtitles:
The Ultimate Guide to Watching Vamshi Paidipally’s "Oopiri" with English Subtitles Oopiri Movie With English Subtitles
Depending on your country, regional licensing allowed Oopiri (or its Tamil counterpart Thozha ) to stream on these global platforms. Check your local library to see if it is currently active. If you're outside India, your options may vary