In your personal account, navigate to Contacts — Lists.
Open the list you need and choose all contacts that you would like to export. To choose all contacts, click on the checkbox in the header next to Email.
Then click on Actions — Export.
Choose the format for your file (XLS or CSV). In the same window, you will find the amount of contacts to be exported.
The link to download the file can be found in the support chat and in your mailbox as well.
Useful links:
Create a Contact List
Delete a Contact List
Copy or Move Contacts Between Lists
See Contact Information & Campaign History
Rename a Contact List
How to Update Your Contact List
How to Segment Your Contacts