Stac Lee is nearest the camera. The route up it would land at the point where sunlight turns into shadow, and then (after a zig-zag) follow the obvious crack heading upwards to the left. When you reach the skyline, turn right and follow the ridge to the top (see
NA1404 : Towards the summit of Stac Lee).
Stac an Armin is actually higher, but is further away. It is fairly clear that the route will follow the right-hand edge, much less steep than anything else.
I am told that landing on Armin is more difficult than Lee, but that once you are on the stac it is much the easier of the two.
The two skerries to the right of Armin seem to be unnamed. The island of Boreray is to the right of them, but just out of shot.