Yes, the documentation is right there on the front page. You put your own test data into the box labelled "Text". Then add your regex in the box titled "Expression". The menus on the left point you to the documentation for all the regex types. What could be simpler?
If you take my original Order Date: \d\d\/\d\d\/\d\d , plus Richard Deeming's reply to me \d\d for the rest of the year, then you should be able to work out what else is needed. And you can test your expression online at RegExr: Learn, Build, & Test RegEx[^].
Since I need the order date, I tried using "Order Date:\s*[^\s]+" per your post above, and it is pulling text after the date, time and AM/PM. So, I would like to pull everything before the date, time and AM/PM.