Find out whether your profession is regulated in Switzerland. If not, then you do not need to obtain recognition of your foreign professional qualification. The potential employer in Switzerland will decide whether to hire you.
The list of regulated professions can be found here: List of regulated professions in Switzerland
If your profession is regulated, contact the corresponding agency responsible for recognition: Agencies responsible for the recognition of foreign qualifications and recognition procedure
If you wish to pursue a regulated profession in Switzerland for no more than 90 working days per calendar year, then you must first declare this intention to SERI. Information on how to proceed can be found here: Declaration procedure for service providers from EU/EFTA states