I switched to Linux Mint 18 at the beginning of this month and am loving it but now need to be able to add photos and grab photos from a Synology NAS that is on the same LAN. I have a 2nd computer in the house which is still running Windows 10 for now, and I used Map Network Drive to select a Drive letter, 'Y', then simply typed \\ipofnas\folderthatIwanttoaccess along with the username and password for the NAS, but I'm not sure where or how to do this in Linux.

I see that I can 'Connect to Server' from the Home folder then select 'Service Type' but I'm not sure which Service Type to pick, maybe FTP? and what to do next.

if windows can reach your nas probably samba will work for you. In that case you need to check this: https://askubuntu.com/questions/4618...-network-drive or similar pages.
Otherwise need to know how that NAS is configured, probably NFS is available too.

I set up as ftp and was am now able to see my NAS and the photo files (jpg), but there aren't any icons or previews of the photos, even with the view setting set to icon, just file names. So in order to view 100 photos in a folder on the NAS I have to open each file individually. What do I need to do to view all of the photos as icons when I open the main folder?

this is a different question. Probably using cifs and/or nfs instead of ftp will solve this issue.

Service Type is Windows Share. The popup window should change and allow you to enter the server, folder, username and password.

There should be a browse network in the file browser which works similarly to browsing the network using the Windows file browser.

Assuming your file browser is Nautilus by default you can only see thumbnails on local filesystems. You can edit the preferences and select show all.