First of all, i want to say, i'm using Odin 3.09 for flashing.
You can get it from here:
<MODERATOR EDIT - MALWARE LINK REMOVED>
I explain how to flash a modem and a bootloader together at the same time. You can follow the steps also for only one of both.
Everything you are doing with your phone is on your own risk. I am not responsible for anything.
So let's start with the flash:
You have downloaded your modem (let's say NB9....tar.md5) and your bootloader? OK, so
1. rightclick on Odin and start it as administrator.
2. Now open the windows taskmaster. End all "Kies" processes.
3. In Odin untick "Auto reboot"
4. For the bootloader select BL and browse to your bootloader file.
5. For the modem select CP and browse to your modem file.
The next step is VERY IMPORTANT
6. Power off your phone
7. Start your phone into download mode by holding Vol down, and power button.
IMPORTANT: DON'T REBOOT INTO DOWNLOAD MODE FROM YOUR POWER MENU! ALWAYS USE THE THREE BUTTON COMBO!
8. Once your phone is in download mode, connect it to your PC. (Best results always with your original Samsung USB cable)
Odin should say "Added" now.
9. Press the Start button in Odin and let it do it's magic.
wait about 2 - 5 minutes.
10. When Odin shows "PASS" you can unplug your phone.
IMPORTANT: WAIT UNTIL YOU SEE "PASS" DO NOT UNPLUG THE PHONE BEFORE!
11. When you have unplugged your phone, it is still in download mode. Just hold the power button about 8 seconds until your phone reboots.
Go to Settings/my device/about phone. There you will see your new baseband.
To check if the bootloader was flashed correct you need a terminal emulator.
type: su (press enter)
Type: getprop ro.bootloader (press enter)
The result shows wich bootloader you have.
THANKS TO: @Wuby986 who teached me many many things.