Put some water on the burner. After the water is boiling, put a bit of salt(very few usually, especially because tortellini are already salty). Then add some tortellini 100 g should be enough for one person.
When the water starts boiling again, you start counting the minutes. After 10 minutes you can remove the tortellini from the water.
These are the usual ways to eat the tortellini: 1 - you can add some Barilla sauce (I would suggest the Basilico or the Napoletana ones); 2- you can add some extra Virgin olive oil, a lot of Parmigiano Reggiano or Grana Padano and some pepper if you like.
You can also prepare a meat or vegetable broth in advance and cook the tortellini in this one instead of using simple water. Personally, this is the way I like the best. In this case the tortellini will be already very tasty eaten in the soup, and you can add some extra Virgin olive oil and Parmigiano Reggiano or Grana Padano if you like