The very first thing you should do:
Read the Flash Documentation. (Click "Help")
The folks at Adobe (Or perhaps Macromedia, I don't know if it was re-written) wrote this massive guide telling you how to use their program.
You obviously don't have to read all of it, but use the contents page to find the bits you need to know.
If you still have questions, use the Adobe website, they have loads of really good video tutorials that will help you get used to it very quickly.
Also I can't count how many good tutorials have been posted to NG, look around and find what you need.