By default everyone is allowed to use 20 CPUs or 20 jobs (whichever limit you hit first).
Use the command interactive, which will request 1 CPU on a free compute node for an interactive session. Use interactive -h to see the other options. For instance, you can use interactive -w followed by the name of the host in order to land on a specific machine.
Use the passwd command.
It's a very good thing to do right after your account on the HPC has been created by an administrator. Or from time to time, when you fancy. Please pick a robust password or passphrase: something combining uppercase and lowercase letters, digits and additional symbols, or even better: a long sentence that will make sense to you (you will be able to remember it easily), but won't be easily guessed by potential fraudsters. Spaces are characters like any other and can be included in your passphrase. In order to change your password, you must be logged in and you must remember what was your old password, because you will be asked for it. Simply type passwd on the prompt and follow the instructions. Please do not worry that "it's not typing anything", since it is an additional security feature on all UNIX systems: as you type a password, the cursor on the screen doesn't move. But be reassured that what you type is indeed taken into account.