No it's not asking to decrypt or sign anything, they're only saying this:
# easy! just run this
keybase push
"Command line" is for Keybase-cli. So I guess you will have to go for next option.
The next one is the same, they're showing a script which I have to enter into a terminal and I tried but nothing happens.
I don't understand why do they make it so difficult, why can't they just ask me to decrypt a file or sign a message to prove that I own that public key.
I think they don't want users who only upload their public keys but want users to upload their private keys too, which I won't do.
Is there an alternate for it, I already uploaded my public key to MIT public server and ubuntu too, so that'll work for now, I think.