reported speech的知識

simple present tense >simple past tense
simple past >past perfect
simple future >' would ' + bare infinitive ...

change most of the modal verbs
can >could
may >might
must >had to
need >need*

change the pronouns
i/you >he/she
we/you >they
me/you >him/her
us/you >them
my/your >his/her
our/your >their
mine/yours >his/hers ...

change the time words
now >then
today >that day ...

Reported speech.
e.g. "The dog is small and cute." said Mary.
Mary said that the dog was small and cute.
"I am busy now" said Tom.
Tom said he was busy then.