You've got a good bike - I think you'll enjoy riding it.
I believe the Navigator has a triple. That means there are three rings on the front - you might begin by shifting that ring to the middle and leaving it there - then only shift the rear rings for the first week or so. You'll be able to get the general idea of shifting without going overboard. When you are comfortable with the gears you can get to leaving that in the middle and only changing the back - then start changing the front, too.
As for breaking, to begin with - try to remember to break primarily on the back wheel (using the right hand).
Both of these suggestions are a great way to start IMHO. But, they aren’t a great way to continue, once comfortable with the bike and riding, start using all the gears and the breaks more efficiently.
Finally, make some adjustments to make the bike fit you as well as you can - or go to one of the places mentioned above. You’ll be much happier if the seat is the right height.
Have Fun!!!