the "hosts." file is a system file that helps redirecting domain "names" to a certain IP.
If you know what "localhost" is, then you probably know that it links to the IP 127.0.0.1 (which is by standard the local host ip).
This is accomplished by adding a line like:
in the "hosts." file
Anyways, back to your question.
The file you're after is, at least since Windows Vista, is usually in this folder: C:\WINDOWS\System32\drivers\etc
the best way to edit the "hosts." file is to;
1. copy the file from that folder and put it on tour desktop.
2. Open up Notepad and drag the file from the desktop into the Notepad window
3. Follow the instruction on the crack readme, IT probably wants you to add one ore more lines like the one I posted above (changing out localhost to adobe servers I presume).
4. Save the file.
5. Just to make sure, make a backup of the original hosts file by either renaming it or make another copy of it somewhere else.
6. Put the "hosts." file from the desktop back to the "\etc" folder.
7. This might require a reboot.