In first place, I strongly recommend you to update to FL Studio 11, which is waaaaaay better than FL Studio 8 (updates are lifetime free).
Then, you can take a look at Seamless' FL Studio Basic Tutorials series, where he explains everything about.... well, you guessed it, about the basics of FL Studio (
link to the playlist)
But to give you a quick answer, you need to link your audio tracks to tracks into your mixer. For this, you select in your channel list (which appear when you press F6) your audio track (there should be a green light at the right of your object), and then you right-click the desired track in your mixer (which shows up by pressing F9) and you click on "link selected channel" > "to this track". Then, on the right side, you can add up to eight effects by clicking the little arrow.
Generally, as Adlez27 said, you can generate automation clips by right-clicking parameters and clicking on "Generate Automation clip". It will allow you automatically modify the parameter during the song. You can create new points by right-clicking the lower part of your automation clip.
Almost all of these parameters are analogically editable, and some parameters are on/off.