Reported speech, also called indirect speech, is a BIG subject.
There are many different points to cover.
Here's just one example:
In fact, we have a very extensive lesson on this subject:
But before you dive into it, I would like to stress one important point:
Yes, there are many points to consider, but there is only one key datum to keep in mind.
When reporting what someone said, above all else, you should definitely use your common sense.
If Sharon told me yesterday, "Today I feel great," then obviously when reporting it, I should say, "Sharon told me that yesterday she felt great."
If at the store the saleslady tells me, "You can find here what you are looking for," then when reporting it back at home, I should say, "She said I could find there what I was looking for."
Remember, that's what reported speech is all about: you are giving information on what someone else said in your own words. And this wording should fit the current situation you are in!
I hope this helps, and here is the lesson again: