External users are treated the same as Google Apps users, with the exception that they will not be able to perform Google Apps specific actions like adding Google Docs, or syncing contacts and calendar items with Gmail and Google Calendar.
First choosing an Insightly URLIn order to use this new functionality, an Insightly administrator first needs to set a unique Insightly URL for external users to navigate to and log in. To do this, go Settings > 'Insightly URL'. Settings is the small gear icon in the top right corner of Insightly.
Your Insightly URL must contain only the characters A-Z or a-z, the numbers 0-9, or the hyphen character. No spaces are allowed and it must be at least 5 characters.If you change your Insightly URL, it's up to you to tell all your users the new URL so they can continue to access Insightly.
Inviting External UsersAfter setting up your URL, you will be able to invite new users by specifying their first name, last name, and e-mail address through Settings > Users.
The invitation email sent to the new user will include a special link that they can click to enter in a password and they will be logged straight into your Insightly. For them to login again in the future, the user will need to type in the Insightly URL you have chosen, and they will be presented with a login screen to enter their email address and the password they set.