where can i post it ??
can i use it in my signature

Yes , u can use your referral link under your signature and i see you're already using it. Nothing's wrong about it.

Yes, in your signature is fine. Just do not create a post in threads with your referral link. The only time it is acceptable to do so is when you are the FIRST to announce the program. After the first post, any other posts with referral links will be considered spam, and you will receive a warning.