Step 1: Go to the Add Contacts option in the Contacts tab.

Step 2: Select Import from CSV 

Step 3: Choose if you want to add it to an existing list or create a new one.

Step 4: Name your list and Click on Map columns.

Step 5: Review your import and then click on Import Contacts.

Step 6: After that, Contacts Import will start. The import of 100 contacts with multiple columns takes around ten seconds. Once the import is Complete the pop up modal automatically closes and your list will appear under the Segments and lists section.