Bootloader and ROM Manger for Captivate S

[markymerlion]

This is my first time on this forum and I am new to rooting a phone. I have a Captivate I897 with Gingerbread 2.3.5. I rooted my Captivate successfully with Odin 1.85. but want to upgrade to Android 4.1.1 Jelly Bean. I downloaded the Rom Manager but states there is no support for this device. What is another app I can use? The instructions state the device needs ClockworkMod Recovery installed with Android 2.3 Gingerbread bootloader. How do I get the with Android 2.3 Gingerbread bootloader? I have been searching all the forums and Google but there seems to be nothing to tell me where and how to download and install the 2.3 Gingerbread bootloader.