It’s not too late to prepare for the entrance exam MA in English program at Delhi University even in the 3 years of your bachelor's. Just be regular at it and keep some important points in mind.
Be well versed in your BA course- Read your text thoroughly and in various aspects. Read diverse critical essays on each text to attain a multiplicity of perspectives. In case you are graduating from a different subject, refer to the BA(Hons.) DU syllabus.
Read History of English literature- Knowing the roots is a basic step. To get an idea of the basic chronology and ages refer to these books:
A short history of English literature by Sir Ifor Evans.
A brief history of English literature by Peck & Coyle.
Indian Literature in English- To get enough knowledge of the same refers to these books:
A concise history of Indian literature in English by Arvind Mehrotra.
Indian writing in English (4th edition) by K.R. Srinivasa.
Gain enough knowledge of literary theory & criticism- For this read:
Beginning theory by Peter Barry
Literary theory by Terry Eagleton
Update yourself with award-winning authors- This is not difficult if you read beyond your syllabus. Some of the awards to keep track of are:
The Nobel prize
The booker prize
Sahitya Akademi Award
Gyaanpith (for Indian regional literature translated into English)
Pulitzer Prize
Apart from these strategies, I suggest becoming an avid reader and reading beyond your syllabus, and also practicing writing book reviews. All this will help you make a way for the DU English Literature program.