First of all u have to del entry from concerned Ledger which u wanna del. then go in main menu > Account info>Ledgers>Alter>Select Ledger which u want to del and there press alt D.
first to confirm the ledger is empty then go to gateway of tally-accounts info-ledger-alter-select the ledger-Alt+d , You can delete only empty ledgers
u can give the authority to user as ther liability in tally with the help of the user name and password to diffrent use and provide them seprate user name and password