I am sorry but you have me confused ?, You are renting a server from Gameservers which will include a control panel and 24/7 support,
I have found that when you are renting a server for a specific game such as Rust it is already installed on that server so that Oxide is already installed, Any additions such as RustiO map, mods and extensions are loaded through the control panel, For instance on my control panel (for Streamline servers) I have a folder called "file manager" so i open file manager/server/oxide/plugins to load new plugins. You dont as far as i know use winrar to install anything on this type of server, to load plugins you go to the Umod plugins pages and browse through the plugins, read the descriptions of what they do and if you want it you download it to your pc downloads folder (or specified folder) then upload it through your control panel, you edit the configs of that plugin to what you want using the same control panel,
I think you should "open" a ticket with gameservers to gain information of what is installed on the rented server if Oxide is not present.
A) gameservers.com led me to umod, so I don't know why you're being an unhelpful yapper.
B) I clearly contacted them and they stated to come here. If you want me to explain every single detail so you can comprehend then be my guess and ask. No need to write sarcastic comments, you prick.