Can't reference system.drawing.dll

i'm trying to resize images with ImageResizer, but keep getting a compilation error

"Error 1 The type 'System.Drawing.Bitmap' is defined in an assembly that is not referenced. You must add a reference to assembly 'System.Drawing"

Searching for a solution i find several similar questions where the solution is to reference system.drawing.dll to be able to handle images, but when i tried referencing it by:

rightclick project -> add reference -> select COM ->find the system.drawing.dll

but this gives me another error saying "the activeX type library system.drawing.tlb was exported froma .NET assembly and cannot be added as a reference. Add a reference to the .NET assebly instead"

And this is where i'm left dumbfounded as what to do next.

Edit:

code where i get the error

public void resizeImage(String originalFile, String thumb)
    {
        ResizeSettings r = new ResizeSettings();
        r.MaxHeight = 200;
        r.MaxWidth = 200;


      ImageBuilder.Current.Build(originalFile, thumb, r);//this is where i get the first error
    }