If you want to do this, see Import Act-On Contacts from a CSV (or if using Marketing Lists, see the List Management Overview).
You can either upload an Excel/CSV file or add individual records one at a time.
- Navigate to Contacts > Other Lists > Account Lists.
- Hover over the Contacts list
- Add records:
- To upload an Excel or CSV file, click the three dots > List Import / Export > Append to This List.
- To add individual records, click Open (pencil icon) then choose More Actions > Add Contact(s).