Did anyone know how to become Buddhist in India??
Depends on which path and where you are getting ordained.
There is no formal method except being ordained at any of the major monasteries. Once you go there, you will first be explained and asked why you want to become a Buddhist (Tantra or otherwise, that's up to you). Then the monks will explain to you about our philosophy. If you are lucky (and have time), you might get to spend the day with the monks; usually about 2-3 days.
After that, the head Abbott will ordain you with the prayers early in the morning. You then may choose to keep a Sanskrit name (it is usually not applicable to Hindus, Sikhs, etc., since they pretty much have the same names anyway) and get your name changed on the legal documents.
If it is what you want, I would advise you to get ordained in a monastery in either Dharmsala (Himachal Pradesh), my home state Sikkim, or in Tawang (Arunachal Pradesh).
You will find a breed of so-called Buddhists who are Hindu-haters. These people are called Ambedkarites and are a political movement of fanatics (like BLM extremists), who have nothing to do with real Buddhism.
Tip: Avoid them like the plague. They aren't real Buddhists by any means.