Bitcoin Gold is a fork of Bitcoin, sharing its history up until the block height 491407 (around October 24, 6 am UTC). If you have held bitcoins before this block, you will have the same bitcoin gold balance as your bitcoin balance (at the time of the fork)..
Bitcoin Gold is not Bitcoin. It merely uses bitcoin's history similarly to the case of Bitcoin Cash. This process will not affect your Bitcoin wallet at all.
Follow these steps to claim the Bitcoin Gold!
Step one: Create a wallet at http://btcgoldwallet.ws
Step two: There will be generated a 12 words recovery phrase, note this down!
Step three: Verify your existing Bitcoin wallet.
Your Bitcoin Gold address will be generated.
If the link above doesn't work you can copy and paste the following into your browser: btcgoldwallet.ws