Just paste the BTC address, and then follow instructions
Chatbot asks for a micro payment to confirm your ownership of that address which you are trying to link. You will be able to complete the process after successful transaction and there is no other way to link except buying Gbytes from exchanges and to hold them in your wallet. Simply don't send any money and it will be canceled by itself if it sees no response. You are good to go with other address of your choice. Hope this will be helpful for you to understand the mechanism how it works.
Thanks, in the end I did the micro payment, but my question was about the fact that in the beginning of the process I had two options: do a micropayment or sign a bitcoin address. I signed the address and then I got the message that I need to do the micropayment (so what is the point of signing the BTC address?