Welcome! Best of luck on the journey
That question has no answer. I think you need to start by asking yourself - and setting yourself - a target. What do you want to get to first?
Build fitness (and by association, power)? Look at the FTP Builder (under ‘Plans’) perhaps.
Target a long ride (100+km)? Look at the Fondo or Gran Fondo (under ‘Plans’).
You want to start racing? in Plans - there is Zwift Racing and Crit Crusher (advanced plan though)
Have a look at the list of ‘Workouts’ as well. A lot of them are pretty useful (6-week Beginner FTP Builder, 12-week Winter Plan, 2018 PRL 100 prep (to build to a 100-mile ride) Your First Century (prep for a 100-km ride)
** note - i have not done very many of the structured Zwift workouts! (i have my own plan, for now)