Please kindly point out any mistake/steps that I missed/broken link/etc.. if you found it. Thanks.

Note: I seperate into 3 parts to prevent confusion, since it's really in 3 part anyway.

PART 1
1) Download XS++ v1.6.8 from:- Link #1(Official) or Link #2(Rapidshare)
2) Create a folder and extract your XS++ inside the folder(to organize better.)
3) Inside the folder of XS++ (THE FOLDER WHICH CONTAINS XS++), create 'files_to_upload' << folder
4) Create 'tpa' inside files_to_upload, and then create 'preset' inside tpa.. etc..
5) THE FINAL OUTLOOK WILL BE: files_to_upload\tpa\preset\system\desktop\flash
6) So as above, you have to create folders inside folder, and then repeat(see above for the names)
7) Download a Flash Menu/Theme from here. Link provided by LEVIATHAN. Thanks levi!
8) Put the flash theme(the .swf file) into the flash folder (the last folder)

Your folder should look like this now
[attachmentid=283991]

PART 2 - polarzbearz's version 1(You only need to do either my version or LEVI's version. It's the same concept anyway)
1) Download myThemeCreator from here. You might need to register as a member there.
2) Open up the theme file you want to associate with the flash menu. In other words, .thm file pointing at the .swf file (I hope you get what I mean, I dont know what is best to describe this)(Example: Everchanging.thm POINTING at Everchanging.swf AS the Flash Menu)
3) Refer to the screenshot below:-
[attachmentid=283966]
4) After the .thm pointing at the .swf, it's time to upload the .thm to the phone (No need me teach for this part I think)

OR

PART 2 - polarzbearz's version 2
1) Right click on the .thm file, open with Notepad
2) Ignore the unicodes, scroll all the way down and find this line.

3) Rename your .swf file to the same as shown in that line.

WARNING: You cannot edit the stuff in the notepad or the .thm will crash

OR

PART 2 - LEVIATHAN's version
PART 3(a) - IT'S TIME TO UPLOAD THE FLASH THEME/MENU TO THE PHONE! YEAH!

1) Open up XS+++
2) TO connect your phone to the XS, first you have to switch off your phone.
3) Click Connect
4) Hold "C" and connect your phone to the PC.
If you get "Found new hardware" at system, you must install the file first. follow the steps below. If you didn't get this and XS detected your phone, ignore the steps below

1. Insert PC Suite CD. Don't install anything, close the Autoplay and leave the CD inside
   
2. When you hold "C" and connect your phone to your PC via the cable, wait for the "Found new hardware" to come out
   
3. Choose "find installing(or whatever its called, i cant remember. just let it find the 'installation file/whatever file from the cd)[and just allow it to install anything when pop out about 'non verified' and the choices are 'CONTINUE ANYWAY/STOP INSTALLATION', choose continue]
   
4. Wait and you will see "USB XXXX" installed
   
5. Proceed with next step
   

PART 3(b) - After you connected... now what?
1) On the 'Flash' tab [See Screenshoot below] Tick 'Customize File System'
[attachmentid=283967]

2) On the 'Settings' tab [See Screenshoot below] choose 'BreakXS'
[attachmentid=283968]

3) And finally, on the 'FSX' tab [See Screenshot below] press 'Start FSX'
[attachmentid=283969]

4) Wait for the upload to be done and when it's done, unplug your phone, start up your phone, change your theme. Viola! You're done after the hell-of-long-steps..