To invite a coworker to your Company, log in to the Account and navigate to the Invitations page via the Company menu. (Note: you are inviting this person to access all of the Profiles for your own Company. See the bottom of this article for a link to instructions if you wish to invite a customer or vendor).
The Invitations screen will show you all of your accepted and pending invitations. To invite the user into your company Account, click the Add Invitation button in the top right corner. If you do not see this button, it means that you do not have the Admin permissions required to send an Invitation to your Company Account.
If you do have the appropriate permissions, you will see a screen that confirms you do intend to send an Invitation directly to your own Account. You may then continue to fill in the details of the User you wish to invite, and when you are finished click the Invitebutton. An email will be sent to the User to claim their Invitation.