Tap the + people button at the top right of the screen.
Enter the individual's email you'd like to invite then click the + button. Then select a role for the soon to be Squad Member by clicking on 'user', and finally tap the send button. You can also import emails from your contacts by clicking 'IMPORT FROM CONTACTS'. Alternatively, you can manage invites from this Squad Invite pop up as well.
Check out Managing Roles and Permissions to read more about each role in squads, pods, and group chats.
Managing Peoples Invites
After you've sent the invites out that you wanted, you can also manage your pending invites by clicking the 'MANAGE INVITES' button. You can resend pending invites by clicking the invite in the list.