Click on the drop down at the top of the Open window (where the name of the current folder is displayed) and you get the whole path to choose from.
Anyway, if you're unaware, here are a couple useful shortcuts for kbd-driven navigation: Command-Down (arrow) to dig one level down the file tree and Command-Up (arrow) to move to the enclosing directory / folder. I use it many times a day all day long.
No I've never thought to Google how to use the Finder - it seems like that one thing that should be super intutitve - I've never had to Google how to use any other filesystem manager, Windows or Linux. Or iOS. Or Android.