If you decide to do an apprenticeship (vocational education and training programme), you need to look for a position as an apprentice in a company. The database on Berufsberatung.ch is a good place to start. It lists all of the available registered apprenticeship positions in each canton. It is possible to do some vocational courses by attending a full-time course at a vocational school.
Interested in an apprenticeship in the Federal Administration? Find one at the Federal Office of Personnel (FOPER).
Find an apprenticeship in the Federal Administration (German)