Google yesterday released its first 64-bit browser for OS X with Chrome 39. (For those scoring at home, specifically it's version 39.0.2171.65.) In addition to the usual security fixes, the latest version of Chrome promises improved stability and performance over its 32-bit predecessor.
Chrome 39 will arrive via automatic updates if you have such things enabled. If not, you can download it directly from Google. After downloading the file and closing Chrome, drag the file to the Applications folder and replace the older item named Google Chrome.
Lastly, you will need a Mac with a 64-bit processor to run Chrome 39. It's likely you have a Mac with 64-bit support; Apple started making the switch to 64-bit processors in 2006. To check to see if your Mac has a 64-bit processor, click the Apple button in the upper-right corner and choose About This Mac. Your processor is listed on the Overview page. Check your processor against the chart on this Apple support page.