On your mobile app, click on the + sign button at the top left corner of your screen and click on Invite People
Choose invitation type 'Members/Guest' then click 'Next'
Enter the email of the person you’d like to invite. You can add multiple emails by separating them using a comma or spaces.
Click the Send Invitations button.
Note: For security purposes, only verified email domain users will be allowed to join your workspace. You can edit email domains by clicking the "Edit email domains" link.