besides that you need to make sure, that the user under which NC is running, can read/write to that NFS store, you can pretty much first mount the NFS volume and then tell the installer, where it should place the data folder of your NC instance.
If you have already installed NC, shut down the the web server, move all your date from your data folder to the NFS mount and adjust the config accordingly. Please adjust the permissions accordingly.
Please be advised that NFS volumes may have some performance implications, especially when dealing with a lot of small files and I can’t vouch for the performance of your Synology’s NFS implementation. We do use NFSm but it is serverd from a SSD-only ZPOOL running on OpenIndiana, which is indeed very fast and which provides a lot of IOPs.