I work for a company which has developed a test automation solution and willing to release the same under GPL. I need to know where all do the company need to register and what is the overall process?
It is probably off-topic here. Perhaps better on open-source.
Beware, I am not a lawyer and your question might be a legal one (too).
(perhaps you want some written permission to do that, e.g. to protect yourself in case your employer gets bought by some external entity)
You don't need to "register" anything. You could just publish your source code, e.g. on github (or elsewhere). Don't forget a license file. Read carefully about the GPLv3 license (notably the GPL HowTo document explains the details). Don't forget to add a GPL license comment in every source file, and to put the (unmodified) text of the GPLv3 license with your code.
BTW, I would recommend to publish your code under GPLv3+ (not just GPLv3 but also future version) but that choice is yours.
NB: publishing some existing code under GPL is technically easy (but you'll better have explicit permission for that if the code legally belongs to your employer). Getting interest from outside users and contributors is much harder.