As an Admin User, you can access the CRM Reports feature to be able to export lead information.
On the Web Portal go to Reports > Leads > apply any applicable filters > Download CSV to the right of the screen.
You can also export a CSV of your Leads from the Smart Table when you go to Sales > View Leads > Export.
A CSV file will be promptly downloaded with a table of your Leads information.
Note: This ability to export information is only available for Administrator User types.