So you have setup Chatter at Chatter.com and want to start adding users. Just click on Chatter and click on the large ‘Invite Coworkers!’ button. This will enable you to add people in your organisation to start using chatter. Just remember you can only invite users with an email address within your domain. So that will be users with an email @youdomain.com. Chatter enables you to create groups and you can add ‘customers’ to these groups. This enables users outside of your company to interact with users of that group only. This is very useful as a way of enabling external users to collaborate with certain groups they have been added to. You still control who gets added to these groups and can always remove someone if the need arises.