How do you want to specify the objects? Like you're going to manually, interactively click on them? Or based on their size, shape, or location? What exactly indicates those two particular blobs in the image out of the 6 in there?
I mean one way is
[labeledImage, numShapes] = bwlabel(binaryImage);
extractedTwoShapes = ismember(labeledImage, [3, 5]);
but I doubt that's what you want to do.