If you are going from a rom to the same rom that has been updated you often don't need to wipe data / factory reset and can skip that step. Additionally you can go even further by formatting system, data, and cache from the mounts and storage menu.
1. From the home menu, select "wipe cache partition" and confirm by selecting yes.
2. Select advanced menu.
3. Select "wipe dalvik cache" and then confirm by selecting yes.
4. Return to the home menu
5. Select wipe data / factory reset and select yes to confirm (This will delete all of your apps, passwords, settings and accounts.
6. Select "install zip from sdcard"
7. Select "choose zip from sd card" or "choose zip from external sdcard".
8. Select the file you want to flash and select yes to confirm. (if you don't see it, swipe the screen or use your volume up and down to scroll up and down )
9. After it completes, go back to the home menu and select reboot system now.