Trying to do OnRconCommand and I need to get the IPAdress and in the docs it says IPAdress but thats for RustPlugin's

IPAddress (not IPAdress) is native to .NET; it isn't specific to Rust or Oxide. If you have standard references set up in a Visual Studio project, IntelliSense should provide this information for you.

But when I put IPAddress in the parameters I get errors. 

What errors and where?

In Visual Studio, the object does not exist. Sort of like IPlayer

You'd need to add a reference to it then as well as the using statement. https://docs.microsoft.com/en-us/dotnet/api/system.net.ipaddress?view=netframework-4.6

https://imgur.com/a/kOShK53

Here is what I am getting

For some reason can't read text on our screenshots. Can you please copy paste it

boop

https://imgur.com/a/kOShK53

Here is what I am getting

Even tho it was painful to read text on the screenshot, I managed to understand it.
Error says exactly what you are supposed to do. Add a reference to the library which contains type you need. If it's .Net original type - you could find which library contains it by simply googling the name of the type. (I bet first answer will be link to MSDN docs)