Note that I do not use Server version OS X so it may be different.. and I always use VPN for remote access rather than SSH.. so I am not entirely sure what that will affect.
In preferences I have set file sharing on.
That will then allow access to the public folder.
Click on the plus below shared folders and add folders to the list. Make sure the permissions list is to read and write.

Click on options and you can add a user for access to the list.
If you tick the windows file sharing that might also help.

Then from another computer in the network (and it should work from remote as well).
You should be able to drop files into the public access directory using any valid login.
And read from it as well.
Which has worked on my networking testing it just now.
BUT from El Capo there is much more security.. and I had to delete and re-add the shared folder..
And it means you have to copy all the files you want the remote user access to have to be copied to the shared folder.. you should also be able to add access to your own folders..
I am guessing on server version this is a lot more complicated and you will need to post the question in El Capo server area.