There are two ways to add/invite new circle members in the app:

First,

• Click on the '+' tab menu bottom of the screen.
• Tap on 'Invite' and share invite code with the people you want in your circle by pressing the 'Send Code' button
• Select the sharing available option on your phone and sent it

Second,

• Click on the 'settings' tab menu bottom of the screen
• Tap on 'Circle Management'
• Select 'Add Circle Members' option under Circle Management
• Share invite code with the people you want in your circle by pressing the 'Send Code' button
• Select the sharing available option on your phone and sent it