i need one more account on this pc how do i add another log in name?

This if for add user:
https://help.ubuntu.com/community/AddUsersHowto

This is for change password:
http://www.thegeekstuff.com/2009/12/how-to-change-password-on-ubuntu/

Ok this is more simple:
1. Open a terminal by hitting CTRL + ALT + T
2. Insert and run this command:
users-admin

3. Create new user here, and change the password at what user you want.

click the top-right button you use to shut down or restart, then click on system settings, then under the system area click on users and groups. to change the password, click on the user you want to modify, and it will give you basic info like the name, what type of account, and whether it asks to login or not. Select change... next to the corresponding item you want, enter the password, then you can change it.