Hello Aashi, you need to apply for colleges in DU through the centralized counseling conducted by the university online. The registration process normally starts in June month each year. You need to submit your best of four % during the counseling. After that, the cutoff for various colleges are released after some days, you can apply for admission in particular college whose cutoff you have crossed. There are about 8-9 cutoffs each year. All of the admission process is online, you only need to go to the college once you have been given a seat. Considering that you have mathematics in 12th class, you can go for Economics and mathematics courses during the admission.