I'm unclear on the declarations for coding of MS Graph

I've seen

Dim MyChart As Object
Set MyChart = Me.ChartName.Object

It worked for awhile, but now I'm getting errors for example on the Legend
Class when I tried to set the Position:

MyChart.Legend.Position = 3

So I've switched to

Set MyChart = Me.ChartName.Object.Application.Chart

Now it seems to be working again without incident.

I want to be clear on which method I should use.  Also, I assume that I do
not need to set a reference to MS Graph.

Thanks.