How to invite other users via the Jira Cloud add-on?
If you have installed Screenful via the Atlassian Marketplace, others will also see the Screenful link in the Jira UI, and when they click it, they are shown the signup form. So you don't have to send invitation emails in order to invite colleagues, although you can do that as well. When they fill out the form, they will be added to your Screenful account. You can adjust their role and permissions at Account-->Manage Users.