Hi I bought the desktop version of Premium (its still unopened). I needed however Home and Biz. Can I use the premium and then upgrade??? Thanks

Yes---you can do that.  All of the desktop software includes all the forms and schedules.   If you want to upgrade from Premium to Home and Business, you can do that from within the program.  There is an upgrade button on the top tool bar of your TT screen.  You can click that and upgrade.  Then you just pay the difference between the price for the software you already have and the higher version.

A word of caution----when you pay for that upgrade---it will ask if you want to pay by having the fee deducted from your federal refund.  If you choose to do that, it will add an EXTRA $40 ($45 in CA) "refund processing fee" to your cost.  Do not do that.   Just pay upfront before you file, using a credit or debit card.