Step 1:

Click「CRM」, click drop bar button and click 「Contacts」

Step 2:

Click '+New Contact' at the top middle part, then it’ll pop out “Add Contact” menu

Step 3:

Input name, phone number(Note: country code must be added, for example 85268019530), and tag/assignee you want to add for this contact(optional), then click 'Save'

Congratulations!👏