Here:
Flash menus consist of a .swf (the menu) and a theme (.thm). In order to display the flash menu, you must FSX the .swf file to tpa/preset/custom/desktop/system/flash via FSX:

1.Connect to XS++ ( here can you find guide and download from xs++ 2 and xs++ 3.1 )
2.Click the FSX tab.
3.Browse into the XS++ directory in your My Documents folder, and in the folder "files_to_upload" put the directory tree: tpa/preset/custom/desktop/system/flash/ .swf files here and /tpa/user/theme/ .thm files here.
4.Wait for the upload to finish, and then you'll have some flash menus!
[Note: XS++ will usually hang on Activating GDFS for a few minutes (usually 2-3), so it is normal]

Now you have some Flash menus on your phone. I recommend that you get a Flash menu pack (contains the .thm files, .swf files, and the directory tree already made), so that all the file paths are correct within the .thm file.