Nabi (Sallallahu Alaihi wasallam) advised us to make a habit of reciting these the Muawwazatain every morning and evening, i.e Surah Falaq and Surah Naas. Allah Ta’alah revealed these 2 Surahs as a means of cure for Rasoolullah (Sallallahu Alaihi wasallam) from the Sihr that was done upon Him.
The method of reciting these 2 Surahs is that one will read each Surah thrice, blow on his palms and rub over his body.
One should read and blow on his children before going to bed as well.
They may also be written on a piece of paper, made into a Taweez and worn as a means of protection.