Don't get your hopes up about this being a place of instruction. It's moreso a place to get help solving problems where you can show code that is troubling you. That said, there are some things that come up often enough to warrant a little copy and paste....
Let's say you create a button symbol. Since it is a button, it is already a self animating object that will react to mouse interactions, but only visually at this stage. The first thing you need to do to make it useful code-wise is to assign it a unique instance name. So you drag a copy of it out to the stage from the library, and while it's still selected, you enter that unique instance name for it in the Properties panel... let's say you name it "btn1"
In AS3, to make a button work with code, you need to add an event listener and event handler function for it. You might need to add a few (for different events, like rollover, rollout, clicking it, but for now we'll just say you want to be able to click it to get a web page to open. In the timeline that holds that button, in a separate actions layer that you create, in a frame numbered the same as where that button exists, you would add the event listener:
btn1.addEventListener(MouseEvent.CLICK, btn1Click);
The name of the unique function for processing the clicking of that button is specified at the end of the event listener assignment, so now you just have to write that function out:
function btn1Click(evt:MouseEvent):void {
var url:String = "http://www.awebsite.com/awebpage.html";
var req:URLRequest = new URLRequest(url);
navigateToURL(req);
}