If you selected Remove Source File: create Symbolic link as the Replacement Option when you created the Migrate / Store Project (see Step 2), in most cases you can transparently open the replaced files from secondary storage by double-clicking the file name.
In some cases, double-clicking a symbolic link generates an error indicating that the file cannot be opened. If this happens, try launching the program associated with the file and opening the file with the program.
Files opened using symbolic links are read-only. If you want to edit the file, you need to save it with a different name on your primary storage.