How do I use and form the imperative tense?

The imperative tense has many uses in Spanish. The main ones are: to give instructions or orders (apaga la tele), to give or deny permission (Si, claro pasa), to call attention to something (Coge más pasteles) and for publicity (disfrute el verano con nuestros)

Imperatives can be formal (usted/ustedes), informal (tu/vosotros), positive and negative. 

To form the formal imperative, take the 3rd person singular of the present subjunctive. To make this negative, add 'no' in front of the verb.

Hablar - hable (usted)   =positive                       No hable = negative

To form the plural: use the 3rd person plural of the preset subjunctive: 

Entender - Entiendan (ustedes) = positive             No entiendan = negative 

To use the positive informal imperative, take the 3rd person singular of the present tense:

Responder - responde (tu)

To make the plural, add 'd' to the end of the verb

Responder - responded (vostros) 

To make these negative, take the 2nd person of the present subjunctive:

Responder - no respondas (tu)           o        no respondáis (vostros)