Basic credentials are comprised of a username and a password. You can also use limit the credentials to specific URLs via the optional URI property.

Password and form data is stored unencrypted within a WebCopy project file.

URIThe URL of the page the password will be used for, relative to the website URL. This field supports regular expressions
User nameLogin user name
PasswordLogin password

The Expression field uses regular expressions. If your search phrase includes any of the ^, [, ., $, {, *, (, \, +, ), |, ?, <, > characters and you don't want them to be processed as part of the expression, you need to "escape" the character by preceding it with a backslash. For example, if your expression was application/epub+zip this would need to be written as application/epub\+zip otherwise the + character would have a special meaning and no matches would be made.