I purchased a website template and it has a flash intro that I am trying to modify. I have the fla file but I don't know how to change the text in the file to customize it to what I need.

You need Adobe Flash (Formerly Macromedia) and flash working knowledge.

I have a trail of flash and have been able to modify the fla file, just can't modify a certain part of the text, never worked with flash before but thanks for the info.

May be the text info are loading from a *.txt file. Tutorial

Try this Flash Kit