Please clarify referencing System.Uri assembly.

I've been learning some C# and using PowerShell a lot lately, but something in PowerShell isn't working out for me, and I cannot find the MS doc that explains to me why.

Please help right quick:

In my PowerShell ISE session, I want to use System.Uri.

In my code, it worked when I specifically said [System.Uri]::method but I wanted something like "using" in C#.  Even after "import-module -name System.Uri" (which worked, assuming that's correct) I still don't have the desire effect of Uri being recognized.

Any tips?