Hello Nabam,
If you are looking for admission in private college then you can take direct admission whereas if you are looking for good Government college like IITs or NITs, then you have to appear in GATE Graduate Aptitude Test For Engineering. You can fill GATE Application Form in month of Sept-OCt and exam will be conducted in Jan-Feb. results will be out in March. After that, In June you can take admission in these colleges.
Good Luck