Note: Unless you JTAG'ed your console, you probably won't have the requirements. Or know what the hell any of this means (Cya leechers) The link for most of them is on free60.
Edit: You don't need April 6th update on a disc if you already have XeLL 1.0
Mod could you please move to modding tutorials.

Edit: It seems the USB way isn't working with xell 1.0. Use an lpt cable to do the first way. It might work if you compiled those files onto a USB and ran It in xell. Try that at your own risk

XBR_4 HAS ARRIVED LADS LETS AT LEAST HAVE SOME PATIENCE AND WAIT TO SCREW OVER COD7. (Not being literal this just updates your hacked kernel without blowing efuses)
What you need for this:

Latest build.py Script from GIT
Hacked Kernel-Image (hacked-image.bin) (The 8955 kernel, your XBR3 image)
Xbox 360 Dashboard Update Version 4532 (HD_DVD_10-2006.zip) (This will be the 9xxx kernel now, substitute this for all 4532's)
wxPirs to extract xboxupd.bin from 4532-Update
Compiled XELL (xell-1f.bin)
1. Checkout free60-tools, extract xboxupd.bin as described above
2. Copy files hacked-image.bin, xboxupd.bin and xell-1f.bin to /tools/imgbuild/ and create a folder "output" there
3. Start build.py with following command
python build.py hacked-image.bin xboxupd.bin xell-1f.bin
4. Finished! Your updated hacked-image was written into the output directory and is ready to be flashed.
Alternative: If you are using XeLL-compile after 31. August 09 you could use the USB-Update feauture.

1. Format a compatible USB-Stick to FAT16/32.
2. Put 'xell-1f.bin' renamed to 'updxell.bin' into the Root of the USB-Stick.
3. Turn on XeLL-Xbox360 with attached USB-Stick.
4. XeLL should recognize USB-Stick and tell you '* found XeLL update. press power NOW if you don't want to update.'
5. Wait for XeLL to tell you '*update done' and plug out the USB-Stick so it won't upgrade on next startup.
6. Reboot Xbox360 and enjoy fresh XeLL

All credits go to Free60, none of this was mine, I just haven't seen it here so I posted it.