"Please eat something."
Translation:Bitte essen Sie etwas.
Check out the lesson tips (you may need a computer if you can't find them by scrolling down on your phone).
Telling someone to do something uses grammar called the 'imperative'. In German there are three kinds of imperative, corresponding to the three ways to say "you" (du, ihr, Sie).
The two informal ones don't need the pronoun (du, ihr) but modify the verb in a specific way:
Iss was! - to one person, informally
Esst was! - to multiple people, informally
The formal one needs the pronoun but uses the infinitive ('standard') form of the verb:
Essen Sie was! - to any number of people, formally
Since learning the imperative requires learning yet more verb modifications, looking them up on a site like Canoo.net will help at first.