Go to My Computer, click the Tool, then Folder Options from the drop down menu.  Go to the View tab and select "Show hidden files and folders" in the advanced settings list.

Install Sync just like you would any other program.  Then follow the directions to sync up a folder in the proper mod directory.  Sync to a new folder in it, not to the mod directory itself.  In Sins, you can find where that is on your computer by going into the mods tab in the options and clicking show mod path.  It will be in one of the formerly hidden files.