A easy way to access CMD is to press and hold the System Key, and press R.
Run should pop up, type in CMD.
You can change the color of the background, and the text, by typing Color 01 - 99 (Select a number between 01-99)
Now what my favorite thing to do is, once in CMD typing in Ipconfig /release which turns the internet off. If you want to turn it back on just type in Ipconfig /renew
Typing in Net User will display the accounts on the computer. You can edit passwords, delete accounts or make one.
To edit a password just type in Net user Username It should ask you for the password, just type in the password, and then put in the new one afterwards.
To delete an account, just type in Net user Username /delete
You can easily make new accounts as well by typing Net user Username Password /add
If you have anything else, just add it.