If you are interested you can write AFCAT exam for Indian air-force on successfully clearing that you exam you are called for SSB . For army you can write CDS in your final year and also after completion of your degree you get a chance for SSB of armed forces through UES(UNIVERSITY ENTRY SCHEME.)

If  you don't want to write an exam, there are three ways for you to get to the SSB :

1. TGC Entry - only for engineering graduates/final year students.

2. UES - same, but I've heard its gonna be abolished.

3. Navy Campus Interviews