Way too much to explain in one post, there is so much knowledge to know about.
Maybe ask someone working at the gym to help you around for the first few weeks, to show you how to do exercises properly and that. If you don't know what you are doing you could easily injure yourself.
Basically compound exercises need to find their way into your program.
These are
-Bench press
-Pull ups
-Shoulder press
-Dead-lifts
-Squats
Then of course you can put in isolation exercises like bicep curls, tricep kickback, leg extension etc. Always start your workout with the compound exercises though.
If your starting out I would suggest having a full upper body day, then rest, then legs/core day, rest, then another upper body day. So you might hit the gym Monday, Wednesday, Friday. People will give you other types of starter programs, you just need to chose what suits you best, I'm just giving you a general idea. After a few months you can experiment with split day workouts (like doing biceps and back on Monday, triceps/chest Wednesday).
You can start off with 3 sets of around 8-12 reps per exercise, you can experiment with those though, they are just a general starting point I guess. 8-12 reps is ideal for muscle growth.
But yeah, there is lots of info on the internet you can read as well.
And don't over do it, you need your rest days