The search journeys in the title bar will allow you to search for journeys that match your criteria and problem space.
Only public journeys are searchable.
The results come back as a board of tiles. Selecting the title of the tile will take you to the dashboard of that journey where you will have the option of just viewing the summary to find a quick answer, or of browsing the entire journey and all of its threads.
You will also have the option of joining a journey if you wish to contribute.
Contributing to journeys earns you reputation and experience for that problem space.