help with tethering to smarty from laptop

Lost my sky internet 4 days ago due to tech problem their side, should be back end of the week, managed to tether to our laptop so back online :-) How is the data charged ? How do we check usage running &the balance , got a new 60Gig package, just wonder if it was on a daily basis?? Info would be much appreciated Thanks in advance :-) Cheers