Won't boot up because asking me for a password how do I reset th ios password for toshiba l355 laptop

You'll need to take this to a Toshiba service centre I'm afraid.

If your looking for the bio's password and you're the owner they may give it to you on request. But if it is a bio's protection initial password (protects unwanted users) then talk to the person you got it from.

There are 2 different levels of passwords.

1) password protection for bio's modification.

2) password protection at the bio's level for user protection.