can some one help me?

ok i mounted and then whern i clik start it says "cant read dc_bios.bin"
do i need bios if yes tell me where can i download them,








ty

ok i downloaded the bios named dc_bios.bin and i started the emulator it started by asking me whta the date and time the i clicked play the it gives me the dreamcast logo and hes back to the same place(date and time config)
what should i do?
after that i exit the emu then got in again then it says that it cant read the "TOC" what is this???