Need Multisite setting up Wordpress Multisite

We currently have a install of Wordpress running on an AWS server. The install and site run great. We want to use Wordpress Multisite to start to create microsite for our satellite offices. Is the best approach to make the changes to the wordpress file and change the install over to multisite? or should we install a separate version of wordpress? I'm not a wordpress expert at all but I do have LAMP admin who knows some. Just need a little guidance.