Hi Friend,

Just follow the instructions or the pictures that you see here: http://www.symbianize.com/showthread.php?t=321834.

So the tutorial has been categorized in different parts:

1. Preparation - talks about where to download the files you need and how to install the flasher application.
2. Flashing the Root File System (rootfs) - you will follow exactly what is written here, step by step.
3. Flashing the eMMC (the internal storage of the N900) - you will follow exactly what is written here, except that you will use the custom image that you downloaded from fayad, because that one is already customized to have either a 5GB or 8GB "home" partition. In other words, you will use the one you downloaded from fayad instead of the one you have downloaded from the "tablets-nokia" website.
4. Flashing the Root File System (rootfs) again with "-R" (restart) parameter - you will follow exactly what is written here, step by step.

The tutorial in that link I gave you even has YouTube videos so that you can visualize what is actually happening real-time...just compare the video with what you are doing/seeing on your computer to ensure that you are on the right track. Here is the video: http://www.youtube.com/watch?v=E1zvRjL-2cM

NOTES:

1. You have to register to that forum site so that you can see the embedded pictures/screenshots.
2. Since your objective is to flash your phone using a customized eMMC image, you can't do the steps for updating the firmware via the Nokia Software Updater because that method is for flashing the phone only with the official firmware.