Know Thy Bike
This is a good ride for either a beginner new to cycling or to anyone beyond that who just got a new steed.
Head out on a safe short looping course with little traffic. Bring along a allen wrench set that fits your stem and seat post clamp.
Warm up for 10 minutes spining easily. Pick an easy gear and stay in that one. Listen to the bike, are there any weird rubbing noises? Any clanking? Any odd sounds? If so get off and investigate.
After warm up shift to a slightly bigger gear and power the pedals slowly to get a sense of how straight your leg gets at the bottom of each stroke. There should be a slight bend. Get off and change the seat post height only slights and ride a bit more. Adjust as needed for rest of ride 'til comfort is set.
Now shift to an easier gear and bring the spin cadence up a bit. Really get the legs spinning and hold that for 5-10 minutes. How do your arms feel? There should be a slight bend in the elbow, neck shouldn't be craning forward too much. Sometimes simply turing the bars up a hair can make a big difference.
After some adjustments bring the bike up to speed and go through every gear. Shift if into every option there is. Pressure every gear standing and seated, work the whole bike.
Spin easy for the last 10 minutes and finish knowing that you can ride long in the future and trust that bike to be there for you.