The negative familiar command (tú) is conjugated in Spanish by adding the suffix "-es" to the third person singular (él/ella/usted) of the present tense, with the letter D showing.
How to do this?
- Remove the last syllable of the verb, which is usually "ar," "er," or "ir."
- Keep only the root[is of the verb.
- Add "es".
An example of this can be seen in the verb "hablar" which means "to speak" in Spanish, when we conjugate it using the negative familiar command in the third person of Spanish we must remove the syllable "ar", keeping only the root "habl" and add the "es", forming the word "hables".