There is now much demand of good quality sperms in India due to the growing awareness of Assisted Reproductive Technique and as a result of this there is a huge demand for sperm banks. As for donating sperms in your nearest centre, search it on internet.
I know of a sperm collection centre and it’s in Mulund W. It is a state-of-the-art facility adhering to ICMR and USFDA guidelines. It maintains privacy and confidentiality so donor and recipient information will be completely protected.
Sperm donation is something I don’t know much about so I can not help you with that. Though I for sure know about some good online donation platforms. They are amazing for charity purposes as well and I like their work.