Go to My Companies, click Actions and select Edit Company.
Scroll down to "Manage Users". Type in the search bar the email of the user you wanted to invite.
Click "Any Status" drop down button to select the status of the person you are going to invite. You can choose to make them an admin or just a member.
Or you can also use the check and uncheck box beside the invited person below.
As for the "Send Invite" button, you can choose this feature to invite as many people as you want. Just type in their emails in the box and separate it with a comma (,).
The "Action" button feature beside each person's email can be used to delete or block the users you want.