Unfortunately, confusion and not being sure what to do are goin to be the story of your life for the next day or two until you've mastered the interface and everything.
I've just got to say that this was a superb reply. I'm new to the game, too, and the interface is terrible,... but it's well worth the effort. This is truly a great game!
It just has a huge learning curve...
Farms are tricky, though the wiki has some great articles on the whole thing. I had a lot of trouble setting up an underground farm, because I couldn't seem to flood it when it was full of rocks (and I had a very slow time getting rid of the rocks!) I recommend that you use a completely-unskilled miner to dig out your subterranean farm plots!
Meanwhile, I planted some crops outside in ordinary soil. You can't plant the same crops as inside, and you can't buy those seeds at embark, but a herbalist will gather seeds while 'plant gathering.' And setting up outside farm plots - a separate one for each type of plant you want to grow - is very easy (provided you're on soil, not rock). You don't have to flood it or anything.
The interface for farming is not at all intuitive, but I think I'm figuring it out. For one thing, it's hard to see what's highlighted on my monitor. There's very little difference in brightness. But pressing 'q' and moving to a farming plot should show you a list of plants that can be grown there in that particular season (the current season should already be highlighted). Just arrow down to the one you want and press enter to highlight that crop. That's it (ignore fertilization, for now).
One last tip: Check out the kitchen stocks screen ('z') to see how many seeds you have. That might help you decide what to plant (though not everything is edible - check the wiki for that).
Good luck! This game is really worth the trouble, I assure you.
Bill