Welcome to BikeForums and cycling. If you're not addicted yet you will be.
Best way to get into cycling? Just ride.
How long? Start out on short rides that you're comfortable with and increase your time/miles when you feel you're ready.
Pace? Whatever you're comfortable with, maybe 12-15 mph. Increase speed when you feel ready.
Cadence? 75-95.
How often? Whenever you can.
Now get out there and have fun.