1. Open Mozilla Firefox Browser.
2. Type URL : http://seleniumhq.org/download/ in your browser. Selenium IDE download page will get open then click on latest Download version link (Here is 2.8.0) as shown in image bellow. click on that link.
3.When you click on latest Selenium IDE Download version link, Firefox will show one popup saying do you want to allow Mozilla Firefox to install selenium IDE or not. Click on Allow button as shown in image bellow.
When you click on allow button, Firefox will automatically install Selenium IDE software. after completion of Selenium IDE installation, it will show one pop up saying Selenium IDE installation completed. you need to restart your browser to use selenium IDE. Click on Restart Now button as show in image bellow.
When you click on Restart Now button, Firefox will restart automatically. now click on Tools menu list displayed in top. you can see there Selenium IDE as shown in image bellow.
Click on Selenium IDE as shown in image above. It will launch Selenium IDE software window as shown in image bellow.