From your main Contacts Screen, you can do actions on individual contacts, or on multiple contacts.
Taking Action on Multiple Contacts at Once
1- Select the contacts by clicking in the check box next to them
2- As Soon as you select one contact, a yellow box appears on top of the contact list with options available.
In the box you can see how many contacts are selected and the different options of action: "Add Comment", "Add Activity", "Add Task" or "Add to List"
Choose the option you want to assign and click on the respective Icon. Any action will be taken on each of the contacts selected.