Well, Sign in to the admin section, import one of your competitions, and... that's it! Events, competitors and schedule, all of that is loaded from the WCA website and you can synchronize it at any moment.
Note: if you don't use WCA registration system, make sure to import registrations on the WCA website, so that WCA Live can load the competitors. You can do it at any point then synchronize.
Okay, this if fun, what about scorecards?
Sure, currently the recommended way is to use Groupifier. Before generating scorecards for subsequent rounds make sure to open the appropriate rounds and synchronize within WCA Live, so the tool knows competitors for that round.
Note: Groupifier is a standalone app, so any alternative could be used in its place as long as it talks to the WCA website in the standardized way. In the future there may even be an app dedicated to scorecards (with many designs) and separate apps for managing groups.
Right! But how do I actually submit results to the WRT?
Remember Workbook Assistant? Right, you may aswell forget about it! After the competition you can use Scrambles Matcher to attach scrambles to results data.
Note: for now Scrambles Matcher generates the results.json you know, but eventually you won't need that =)