Learn French: Il faut que tu saches mettre le gilet pour attendre les secours. - You must know how to put on the vest to wait for help.

The phrase Il faut que (It is necessary that / You must) always triggers the subjunctive mood. The verb savoir has a highly irregular subjunctive stem, sach-, which gives us que tu saches for the tu form.

Where is the word for "how" in saches mettre?

In English we say "know how to do something", but in French, you never use comment (how) in this structure. You just use savoir followed directly by an infinitive verb. Here, savoir mettre simply means "to know how to put on".

Why is attendre in the infinitive here?

It follows the preposition pour. When pour is followed directly by an infinitive verb, it means "in order to" or simply "to". So, pour attendre translates to "in order to wait".

Why is "help" translated as the plural les secours?

While English uses the singular uncountable noun "help", the French term les secours specifically refers to rescue or emergency services (like paramedics, the coast guard, or mountain rescue). It is always plural in this context.