Pesonally, I use Windows ftp to transfer files. I’m more familiar with it and it is easier to deal with, imo.
You just need to setup a new network location with your ftp details. Those can be found in your admin panel in the config section.
I have heard that some people prefer to use Filezilla for ftp.
I agree with roughtimez, you should install Oxide. Magma is yesterday’s mod manager.
Once you have installed Oxide through the Gameserver’s control panel, run the server once to generate the config files. The config files are where you edit the mod settings.
These files can be found on your server’s root directory in the oxide folder. The mods go into the plugins directory and the configs are in the data folder.
I use Gameservers to host my server as well. Their customer service is top-notch.
If you decide to use Rusty, the remote rcon tool, and are able to get it working; please let me know here. I have been having problems with that program and no one can give me a straight answer on how to get it working.