Clean the beam or joist the stud attaches to. Dust it with a dry or slightly damp rag to remove any buildup. Remove any severe dirt with a damp sponge and several drops of liquid dish detergent. Let the beam fully dry before attaching the stud so the rubber doesn't trap moisture under it, which can lead to mold or rotting over time.
Measure the width of the beam or joist with a tape measure. The rubber stud should be wide enough to fit over it but tight enough to form a tight seal. Cut the rubber with a sharp razor blade to widen it as necessary. Wear protective gloves to prevent cutting accidents or injury.
Push the rubber stud over the beam or joist and tap it with a rubber mallet to ensure it fits on tightly all the way. A loose stud is not as effective at sound proofing.