Hi Stef and welcome to the forum! And welcome to the AutoCAD
There are tutorials on this site that you could start with (Tutorial button at the top left corner). The tutorials on we-r-here.com/cad/tutorials get recommended by users here as well.
If CAD is something you are planning to continue with, there are classes you can take (depends on where in the world you are, where in the world are you?) and there are also books that you can buy. For instance the author Ellen Finkelstein both has a website and books that can help you.
And lastly, you have signed up to the best (*polishes nails on shirt and looks at them*) cad-forum there is. This one that is
Ask as much as you need, it's always best to start a new thread for each new question (or question-group) so that the converstions don't get too convoluted. And remember there is always more than onre way to skin the cat so don't be surprised if you get five different solutions for even the easiest task. Especially for the easy tasks...
Like lines. You can find the button for a LINE. Or the button for a POLYLINE. or the button for a RECTANGLE. They all pretty much get you the same thing. I would recommend that you start with some of the basics tutorials and then play around a bit with AutoCAD and see what you can find. And if you get stuck, come back here and ask questions.
Now, I will shut up and go get some coffee