// Load the base layer
ImageEnView1.LayersCurrent := 0;
ImageEnView1.IO.LoadFromFile('bordermap.png');

// Give the base layer a name:
ImageEnView1.Layers[0].Name := 'Border Map';

// Make the 'bordermap transparent (because you want it on top of other maps)
ImageEnView1.Proc.SetTransparentColors(TColor2TRGB(clBlack), TColor2TRGB(clBlack), 0);

iLayer := ImageEnView1.LayersAdd;
ImageEnView1.IO.LoadFromFile('RainFall Radar Image.png');
ImageEnView1.Layers[iLayer].Name := 'RainFall Radar Image';

//To move the baselayer (0- Border Map) over the RainFall Radar Image (layer 1) use LayersMove.
if (ImageEnView1.LayersCount > 1) {Layerscount should be 2 now) and (ImageEnView1.Layers[0].Name = 'Border Map') then
 ImageEnView1.LayersMove(0,iLayer);