Regarding saddle height...
Sit on the saddle. Raise it's height until there is a slight bend in your knees when your foot is at the bottom of the pedal stroke. You'll adjust this a bit at a time till it feels right. Very few...if anyone, gets this right first time.
You'll have more than sore knees as the miles increase. It's perfectly natural. Just your body getting used to working in positions it isn't used to. They aches and pain will disappear fairly quickly...unless you fall off alot

When riding, keep about 3 feet/1 metre away from the kerb. Initially, keep your rides to your local streets and quiet road until you get used to the bike.
Enjoy it!