How can I enable auto-rotate for the home screen?
If it doesn't work out of the box, which is the case with many Android phones, then you have a  few different options:


A launcher replacement which adds this feature (may not work with all ROMs)
A custom ROM like cyanogen mod, which has this feature built in. You can read more about custom ROMs here 
Wait for an official update which adds this feature. (may never happen)