On the "Formulas" menu, there is an "Insert Function" icon. If you use this to enter your formulas, it tells you what each "argument" (the values separated by the commas) represent.
Just pick your function, and it will help you fill it out. And most have a "Help on this function" link, which takes you to documentation with examples.
Also, doing Google searches on specific functions also yields a lot of helpful information. For example, do a Google search on "excel and function", and see what pops up!
And of course, feel free to ask us anything that you cannot figure out on your own, espeically if you would like us to explain some formula that we are using.