You've listened to a net, your radio is programmed, you've said hello once. A net is the easiest transmission you'll ever make, because someone is explicitly asking for you.
Before it starts
Find the net on the nets page and be tuned in five minutes early. Have your callsign written down in front of you, phonetically. Yes, really - the first time, the brain goes blank.
KI5QRT → Kilo India Five Quebec Romeo Tango
When to speak
Net control will ask for check-ins in groups. Listen for the one that fits you, and if none does, wait for the line every net has near the end:
"Any late or first-time check-ins?"
That's you. Wait for the courtesy tone after NCS finishes, then key up.
What to say
"Kilo India Five Quebec Romeo Tango, KI5QRT, Priya in Norman. First-time check-in, no traffic."
That's the whole thing. Callsign phonetically, callsign plainly, name, location, and whether you have traffic (an announcement). "No traffic" means "I'm just here". NCS will acknowledge you - often with a welcome - and move on.
If NCS asks you something
Answer briefly and end with your callsign. If you don't understand the question, say so: "Say again for KI5QRT?" Nobody expects polish.
Afterwards
Come back next week. Nets are how a repeater becomes a community, and after three or four check-ins people will know your name. When someone asks for volunteers to run the net, that's a very good time to say yes - being NCS is the fastest way to learn every callsign in town.
Then mark this path done, and tell someone else where to find it.