Quitting a Job or Training
Quitting any job or training is very easy; you just have to write two lines on paper stating that you are resigning and request relieving. Then follow the process of clearance and relieving as informed by the HR Department.
More importantly, you should make a decision about quitting after due deliberations. I am not sure why you are quitting. I do not see any substantial reason for quitting. If you were to quit within 3 months, then why did you join Infosys in the first place? Consult seniors, friends, and family members before making any decision. Are you sure you have a better option by quitting Infosys? I feel your opinion will not have much depth and value in this case, since you are young and inexperienced. You should definitely seek the opinions of seniors and those with long industry experience.
Relieving Formalities
Regarding relieving formalities, contact Infosys's HR Department, and they will guide you through the process.
Financial Obligations
Do you have to pay any money? The answer is to go through your appointment letter; surely, you will find a relevant clause there. Otherwise, contact the HR Department to have clarity on this.
Thanks & Regards