Dear aspirant, Delhi University (DU) is one the most prestigious universities in the nation and getting in there is highly competitive. NTA conducts DU entrance test (DUET) for admission to DU. You can check more about it here-

https://engineering.careers360.com/articles/du-btech

Also 63 percentile won't  help , as there is a lot of competition of aspirants to get into DU.

Dear aspirant,

As you have mentioned that you want to do BTech in du do let me tell you the admissions are through JAC counselling. In this colleges like DTU ,NSUT delhi ,IIIt delhi are there.

Now coming to second part of the question , you have mentioned that you acquired 63 percentile in jee mains so considering you as a general candidate, there is no chance for you getting the premier colleges in delhi . You need to increase your percentile in the next two attempts. You need to score atleast 97+ so if your home state is delhi then it would be better for you to get premier colleges and if you are outside Delhi then you need atleast 98.5+.

For more information you can check out the link given below-

https://engineering.careers360.com/articles/du-btech