Are wall anchors necessary for hanging a small speaker?
I agree with @user263983. Use plastic drywall anchors that go with the size of flathead screw that fits properly into receivers on the backs of the speakers. The heads of the screws must be small enough to fit inside the bottoms of the slots and large enough to be retained in the smaller tops of the slots.
Drill square to the wall so the screws are perpendicular to the wall. Drive the screws in so that the bracket just barely slip fits between the underside of the screw head and the plastic anchor or the wall.
If you don't have a drill or don't want to drill, there are anchors with a sharp end that you force into the drywall and then twist with a screwdriver to pull into the wall. Get the right size, and use two for each speaker. Self drilling drywall anchors