You can import contacts anytime by clicking Import Contacts in the left sidebar.
From here you can choose to upload a CSV file or connect to an integration to automatically update your data.
If you choose Upload CSV File, you'll see the option to bulk import multiple contacts at once.
You can also add contacts one at a time by clicking + Manually Add Contact in the Import Contacts sidebar.
When you import a new CSV, it may take up to 15 minutes to fully sync into your account. There are a few things happening in the backend:
Email addresses are validated
Invalid or outdated email addresses are flagged
Any duplicate subscriber profiles are synced
Publicly available data like full name, gender, location and age is added to individual subscriber profiles
Note: Any data you import is only available to you and any admins you've added to your account.