What does the xmlns need to be to use a custom control?

I want to customize the Label control to do some formatting of the text. I can write the C# code to do something, but am having trouble getting it to compile with the custom label in the xaml.

Here's what I have:

xmlns:custom="clr-namespace:myAssociation;assembly=myAssociation"

Then when I try to use it I have:

<custom:CustomLabel x:Name="lblUsername"

My class is:

using System;
using System.ComponentModel;
using Xamarin.Forms;

namespace myAssociation
{
    public class CustomLabel : Label
    {
        public CustomLabel ()
        {
        }
    }
}

And my renderer:

using System;
using System.Drawing;
using Foundation;
using UIKit;
using Xamarin.Forms;
using Xamarin.Forms.Platform.iOS;
using myAssociation;
using myAssociation.iOS;

[assembly:ExportRenderer (typeof(CustomLabel), typeof(CustomRenderer))]

namespace myAssociation.iOS
{
    public class CustomRenderer : LabelRenderer
    {
        protected override void OnElementChanged (ElementChangedEventArgs<Label> e)
        {
            base.OnElementChanged (e);
//          my code
        }
    }
}

When I attempt to compile I get the error:

The type or namespace nameCustomLabel' does not exist in the namespace CaliforniaMedicalAssociation'. Are you missing an assembly reference? (CS0234) (myAssociation.iOS)

I can't find documentation on how to include a custom control in xaml nor can I figure out why how to get around this error!

Thanks in advance!