Navigate to the Users page
or the Invites page:
Click on the email icon:
This will bring up a modal where you can add the invitee's email. At present, you cannot bulk invite, however there are plans to implement that in the next release:
An email will be sent to the email you entered, with a one-time link. If the invitee clicks on the link, their browser will open at the ApiOpenStudio administration site.
They will be asked to click on the "Forgot password" link. This will generate another email with one-time password reset password link When they click on that link, they will be redirected to the ApiOpenStudio administration site, where they can set their password for final API access.
They will not have any access to ApiOpenStudio resources (unless you have created resources that only require an active token) until you give them a role. They will be able to login to admin panel and edit their own details, however.