Step 1:

You have to Add a button to the first frame of your flash movie and convert it to a MovieClip symbo see here

Step 2:

Then Name your button “User defined” using the instance name box at the lower left

Step 3:
Then go to layer option or click the new layer button in your working window Create a new layer called script.

Add the code provided below to the first frame on the script layer:

"your button name".onPress = function() {
    // When button is pressed, go to the provided link
    getURL("http://www.iiuniveadds.com");
}

You can also open the link in a same window , child window, new browser window by using..

• Open your button and add a second frame to the timeline.
• Modify the button appearance on the second frame

Code to add a rollover to a flash button:

"your button name".onRollOver = function() {
    this.gotoAndStop(2);
}

"your button name".onRollOut = function() {
    this.gotoAndStop(1);
}