I have some BTC from grid mining I did 6 yrs ago...all I have now is the bitcoin address. How can I spend it?
You can't. An address is not enough to spend coins. You need the private key that corresponds to that address; if you don't have that, then you can't spend the coins. You cannot get the private key that corresponds to an address by only knowing the address; rather you must have had that private key since it was generated and never lost it since then. If you do not have the private key, your coins are lost and unrecoverable.