I'm 6'4". My recommendations are as follows:

What's most important is whether the bike fits you - a good fit will do the most for maximizing your riding enjoyment. I suggest that you go to a bike shop that offers a fitting. Yes, you will pay some $$ but it will be worth it. Take your bike with you - the mechanics can determine if they can make the necessary adjustments (saddle height, stem length, handlebar width, crank size, etc.). You may find that they can't get it to fit you - if that's the case, then you're better off getting rid of it (donate it!).

After you've got a bike that fits, make sure you get a decent helmet and learn how to adjust/wear it properly. If you ever get involved in a crash (crashes can be caused by a multitude of things - collisions, slippery surfaces, pilot error, etc.)

Start out easy - relatively short distances. As your confidence and stamina improves, try challenging yourself at longer distances. But then you're going to need to be more independent - take tools you'll need to fix a flat (learn how to remove a wheel and fix a flat at home before you're stuck out on the road somewhere!). Be sure to take a water bottle and drink!

In time, you'll learn other things that most of us already know, but don't want to overload you!

Good luck and have fun!