When you click the Sync Sets link, you will be directed to the Act! Sync Sets Databases page. 
This page will list the Sync Set Name, Status, All Users, Description and Action that can be taken.  
You can click on the Sync set name or the blue edit button under the actions column to edit the sync set. Here you can edit the name and description of the sync set.  You can also edit the users of the remote database and add or remove users from the sync set.  
To add or remove users from the sync set, use the arrow keys above the user list.  You can add or remove one user at a time by click the single arrow, or you can add / remove all the users by click on the double arrows. 
You can also specify which contacts will sync.  You can either sync all the available contacts or you can define the data you wish to sync.  If you like to sync a defined query, you can select it from the drop down.  
Once you have finished editing the sync set, click the blue save changes button at the bottom.