Yes. The way to boot into this to apply any changes, and don't go hog wild yet, is to power phone off, hold down the power, home and volume up button, wait for the second Samsung logo to flash, then let go. Then you'll see what is CWM.. in yellow writing I presume. My recommendation before flashing anything is to wipe your phone.. make sure your important information is backed up, like your contacts and such. I use backup assistant for that, but another good app for that is Titanium Backup. I prefer Backup Assistant and then Mybackup Pro for my apps and such.
Flashing the file will be under install zip from sd card > choose zip from sdcard. You'll use your volume toggle button to scroll, and your power button to select your choice. If you are installing Gummy, you'll want to completely wipe your phone, per his instructions.. and is necessary imho when flashing a new ROM. You can also flash a new kernel.. I'm using the PBJ kernel and works pretty nice.