"Gee, why can't it be as simple as downloading it on a flashdrive and then uploading in new computer...but no it must be more complicated. Please let me know how to do this".
It is that simple!!
From you old computer in FTM do a File>Backup.
Make sure you tick the include media box
FTM will produce a .FTMB compressed file including all your media
Save this .FTMB to your hard drive and then using Windows Explorer copy it to a USB drive or CD
(Note you can do this direct to a USB, but with a big file with lots of media it can be a bit slow).
Now take the USB to the new computer
On the new computer again using Windows Explorer create a new folder. Call it what ever you like [say] "My FTM files". It doesn't matter where you create it or what you call it.
Now using Windows Explorer copy the .FTMB file from the USB to the new folder.
Now the final bit
Open FTM, and do a File>Restore. Navigate to where you have saved the transferred file select it and press open.
FTM will uncompress the file and relocate and link all the media correctly.
Don't forget with your FTM on your new computer to register the program and if you have an Ancestry membership login using your Ancestry user name and password