http://www.wordreference.com/conj/EsVerbs.aspx This web site shows you how to conjugate verbs for ustedes (for men, women or both), pronoun used in Mexico and vosotros (for men or men and women mixed/together) and vosotras (only women), pronouns used in Spain. So "ustedes" means the same to "vosotros/vosotras", the same for their conjugations. Ustedes is conjugated just like "ellos" and "ellas" in the web site appears as Uds, wich is the short for "Ustedes". Spanish from Spain is only used in Spain, whereas mexican one is used in whole Latin America and it is recognized as the most important in Latin America and in the USA due to one in four spanish speakers in the world lives in Mexico.

Si te refieres a cuando es presente o cuando es pasado, necesitas practicar conjugando verbos en presente para que practiques, después seras capaz de ver la diferencia. Suerte !

thank youu :)

¿Que es lo que te confunde? Yo tengo - Tu tienes --> Yo tuve- Tu tuviste