I have never transfered contacts from computer to cell phone but truenorth's advice seems most likely right on target.
I do not believe you'll be able to import directly from the Excel file to your cell phone. My guess is that you will need to import the Excel contacts list into the software you install, the software suggested by truenorth. Once you get the contacts data into the software on your computer, then you can proceed to transfer the contacts to your cell phone or, in other, synchronize your computer and phone.