Being a 1st year, you have 7 courses which you are REQUIRED to take to graduate to 2nd year. 

These courses are:- Astronomy, Charms, Defense Against the Dark arts, Herbology, Transfiguration, History of Magic and Potions.

Now let me explain how to get to your courses. 

On the menu bar above check the courses bar. A drop down box will appear. Click on the second option called Course Directory. 

Then you will see the different year 1 courses. 

Click on any 1 course you would like to start with. 

(Personally, i'd say don't start with Potions for it involves 10th grade physics so if you're younger then save that for the last.)

When you click on a course, it will take you to a page describing the course. exactly to your right, you will see a sign saying 'Join course'. Then you will be able to join. 

Read the lessons thoroughly and after done, go to the right hand top corner and check the lesson assignments and complete. 

Also take notes for the lesson on notepad or something. 

After taking notes, go to the courses drop down menu and click on the notebooks option.

Store your notes there.