The easiest way to move your subscribers/recipient list from another platform (ie. MailChimp, Campaign Monitor, etc.) to Approach is to export a CSV or XLS file from the other platform.
The CSV or XLS file will have columns of all the data you need (ie. Name, Email, etc.).
You can then import this CSV or XLS file into Approach in the Recipient List tab. Here is an article about importing a file into your Recipients List.