Vayomer is hu amar, in english means “and he said”. “
A perfect example of the “Vov” hamehapechet, that when placed at the beginning of such a word, changes the meaning of the tense of the word either from past to present or present to past. “V’amarti” would then become, “I will say.”
There are, of course, some exceptions to this rule, where the Vov actually means “and” and the tense is correct otherwise. I have found that this usually signals to me some kind of drush-ie meaning, whereby one can extrapolate a “future” meaning for the generations, even though the sentence is meant to be a reference to a past occurrence. Kind of like the idea that history repeats itself.