To add members in the group dashboard, please follow the below mentioned steps:
Group Dashboard // Member // Add members // You will see three options to add a member
Add member feature allows you to add members from the dashboard. If the number of members are high, you can upload a CSV file (sample file is given). For a single member, you can select Add member via widget and proceed with the membership selection, adding the member details and then either make payment online or send / generate a payment link.