1. Go to Marketing > Email > Contacts and click Upload Contacts (or open a list and click Upload Contacts there).
2. Click Download Template to get contacts_template.csv; the header row is name,contact. Fill one person per row: name and contact (the email address). You may add a third column receiveemail with 1 or 0 (defaults to 1).
3. Click or drag the file into Click or drag a file here to upload (.csv files only) and press Import Contacts.

The file must be .csv; comma, semicolon or tab separators are detected automatically and a UTF-8 BOM from Excel is handled. Rows with a missing name or email, a different number of columns, or an email that already exists as a contact are counted as errors. The result reads Imported success X lines and Y lines with errors! (on a list page: Imported X new contact(s); Y contact(s) added to Z list(s).). When uploading from a list you choose under Add uploaded contacts to which lists receive the contacts (existing contacts are linked too); uploading from the Contacts page only adds them to your main Contacts.