How to make a Button that redirects to a link in Actionscript 3.0

Since the situation is a little unclear, I will answer based on some assumptions.

Since you mentioned AS3, are you publishing as an AIR application (Desktop, Android, or iOS)?
If you are using HTML5 Canvas instead of AS3, please let me know your Publish Settings.

Here, I will proceed under the assumption that you are using AIR for Desktop and that a button symbol is already placed on the stage.
If you are unsure how to create a button in the first place, please let me know in more detail.

First, have you assigned an instance name to your button symbol?
If not, please assign one.
You can set the instance name in the Properties panel.
For this example, I will assume the instance name is set to btn01.

Next, click the frame where btn01 is placed, and open the Actions panel.
You can also press F9 to open it.

Here is an example where clicking btn01 opens https://www.adobe.com/jp/ :

btn01.addEventListener(MouseEvent.CLICK, url01);
function url01(evt:MouseEvent):void {
var goURL:URLRequest = new URLRequest("https://www.adobe.com/jp/");
navigateToURL(goURL, "_self");
}

On the first line, when btn01 is clicked, it executes a function called url01.

btn01.addEventListener(MouseEvent.CLICK, url01);

Then we define what the url01 function does.

function url01(evt:MouseEvent):void {

We specify the URL we want to open.

var goURL:URLRequest = new URLRequest("https://www.adobe.com/jp/");

Then we open the specified URL.

"_self" means it opens in the same window.

Please try this method.
Let me know if it does not work, and share more details about your setup.