Employment Agreement Breach Clause - Contract Breach - Wenzhou Human Resources Network

I am a graduating student. Since I didn't clarify to the employer that I was planning to take the postgraduate entrance exam when I signed the employment agreement, now the employment agreement is still with the employer (the employer hasn't sent it back to me), but I've been admitted to a graduate program. Now I want to explain the situation to them, what should I do? Will I need to bear relevant legal responsibilities?