Whether hanging pictures or securing shelving to the wall, it is never recommended to simply use screws, because of the soft drywall compound. Over time, the screws will widen the hole they are in and back out or fall out, which is obviously not what we wish to happen. Using drywall anchors is a fast, safe, sure way to ensure that the screws will remain where they are for a long time to come.
Use a drill bit that is the recommended size on the packaging of the drywall anchors. If there is no access to the original packaging, the trick is to hold the anchor up to different drill bits until there is some anchor visible around the bit, ensuring that it will actually anchor to the wall.
Decide where the anchor is to be placed on the wall, and drill a hole in that spot. Keep in mind that some measuring may be necessary for this step, to ensure proper height or a straight hang. Also, be aware of where wiring is behind the wall so it is not drilled into.
Tap the drywall anchor into the hole, either using the butt of a screwdriver or a light hammer. Do not shove it too far into the hole, as the anchor will open once the screw is inserted anyhow, so there is no need to over secure it at this point. It should be snug and not wiggle in the hole.
Install the screw into the drywall anchor. This final step, as mentioned above, will complete the process of anchoring it into the wall, because the anchor expands in the hole.