I will explain to you some definitions first
1. Custom recovery will overwrite your phone stock recovery. It has many features that stock one does not. Such as: backup/restore your rom, install custom zip/ota update (install custom kernel, custom rom) and many more...
2. According to 1. To install a custom rom, you must have a custom memory first, right? Because custom rom mostly is packaged in a zip file. You can't use Odin to flash it as you did with a stock firmware
There is no chance you will brick your phone mate if you do the following instruction carefully. Provided that, you have your custom rom put into your internal memory or sd card.
1. Use Odin to flash Philz Touch recovery. Its steps are exactly as the same as you root
2. After flashing Philz Touch, your phone will automatically reboot, turn off your phone after that
3. Now, enter recovery mode by pressing a combination keys as I said above
4. After a few seconds, you will see recovery menu.
5. Choose wipe data/factory reset - > clean install a new rom
6. Choose install from zip - > install from sd card if you put your custom rom in internal memory OR install from sd card 1 if yours is in sd card - > choose the rom and install. Follow its instruction and reboot