Wiki properties are created simply by typing a property name and a colon at the start of a line. The value is everything else on the line. Look, for example, at the top of this page. There's a property called Summary and it's got a value of this page provides information about properties

For properties with multiple values (e.g., Keyword), use commas to separate the values. For example:

Properties are a rich and powerful mechanism. This short page provides information about how to create them, but there's much more information at WikiPageProperties.