If your tracker is linked to the Index:

1. Add a row
2. Hover your mouse over the new cell under Index Link and select Link Folder

 

If you want to granularly link documents and folders to a row, first create a new column. Any number of folders, filerooms, and files can be manually linked to a row:

1. Click Columns above.
2. Click Add Column.
3. In the Column Type drop down, select Link to Index, and name the column.
4. To use the new column:

1. 1. Click in a row's cell. 
   2. Select files, folders, or filerooms via checkbox.
   3. Click Done.