Questions & Answers about Alkalmazzuk a szabályt.
The verb is alkalmazzuk.
Its dictionary form is alkalmazni, which can mean to apply, to use, or in some contexts to employ. In this sentence, it means to apply.
Hungarian often uses the first person plural imperative/subjunctive to express English let's ....
So alkalmazzuk can mean let's apply it or, with the object stated, let's apply the rule.
A useful thing to know is that this form can also look identical to we apply it. Context tells you which meaning is intended.