In this article about the infinitive form you can read about its various usages in Italian.
If you look at point c) you can read
c) Per dare istruzioni di tipo tecnico: (in order to give technical instructions)
Mettere il burro nella terrina e mescolare con cura.
In this case you are giving the instruction to follow in order to perform a recipe.
Also in case d), from the same source, you can read another context of use:
d) Negli ordini espressi in forma generica: (when giving orders in a generic form)
fare attenzione, tenere la destra, rallentare
Circolare! Circolare.
Also in this similar article (thanks to @TadVogatt) you can read about the usage of the infinitive form in Italian.
In particular:
The infinitive can also serve as the equivalent of an instruction, in
cooking for example:
Cuocere per tre ore. Cook for three hours.
Tenere a bagno per 30
minuti. Soak for 30 minutes.
Lavare e asciugare l'insalata. Wash and
dry the lettuce.