To do either of those, make your pointer click on the User icon (the 3rd icon from the bottom) in the Admin Panel and click Ban rules.
Click Add new to add a new ban rule.
Enter a reason in Ban name / Reason field.
Enter either an IP rule or an E-mail rule.
To replace unknown characters use * (the asterisk) symbol.
When you're finished, click Add new ban rule to save your changes.