How to access network pc without password

Well, you can't - at least not if it's password protected. That's what passwords are for, isn't it?

Perhaps if you explained a little more about the circumstances and what you are trying to achieve. But if a computer - any computer - is password protected and you don't know that password then you can't access it. Well, not legally anyway. That is treated as computer misuse and carries a jail term under many juristictions.