There are various ways to give a command or an instruction. Simple Polite commands are the most formal, as they use the Usted ( singular) and ustedes (plural). 

In order to form the simple polite command begin with the I or Yo part of the verb.

AR verbs

 e.g. hablo.  Remove the O leaving habl and add e for usted – HABLE

 e.g. hablo.  Remove the O leaving habl and add en for ustedes – HABLEN

ER verbs

e.g. como.  Remove the O leaving com and add a for usted – COMA

e.g. como.  Remove the O leaving com and add an for ustedes – COMAN

 IR verbs

e.g. vivo.  Remove the O leaving viv and add a for usted – VIVA

e.g. vivo.  Remove the O leaving viv and add an for ustedes – VIVAN

To make the command negative simply place NO before the verb.

E.g. NO hable / NO hablen.