The answer actually turned out to be pretty obvious. I'm new to linux, so I was confused. When I logged into the server using the username and pw that I used to install the server, I was under the misunderstanding that this was the same as being root.

Anyway, I didn't have the correct permissions to edit the file, so to fix it I used Putty to ssh into the server then I created a new group called editors with the following code

sudo addgroup editors 

then I added my user to that group

sudo adduser myusername editors

Next I gave the group editors ownership of the directory

sudo chown :editors /etc/ssh/

Next I changed the file permissions such that the group could write to the folder

sudo chmod 770 /etc/ssh

After logging back into the server again with WinSCP I was able to edit the files in the directory.

This may not be the recommended way of going about this- if it isn't I'd appreciate someone letting me know :)