You will have to wait until BitcoinGold releases the Coins on Nov.1st . If you hold Bitcoin BTC on Oct.25 you will receive an equal amount 1:1 of BTG Bitcoin Gold. The video in the link explains which wallets and exchanges to avoid, as they may not allow access to the new coins.
The best advice, is to store your BTC Bitcoin on a cold wallet, or external wallet. You can also find exchanges that will be allowing users to withdrawal BTG after the fork. You can also wait until November as exchanges may open up trading of Bitcoin Gold as time goes on.
RE: BitcoinGold Hard Fork | 48 Hours Away! HD Video