Optimizing your image in your website is useful to make better performance when is loaded. Here the simple way how to make it. First you have to download the software GIMP. Its the one software I recommended to you because its so light and easy friendly to use.
When you create or modify image with such as photoshop, the result image that you save its not really optimize. So, you have to optimize again with this software. Just open your sphotoshop image and open it by GIMP, when GIMP is opened then save it again. Make it sure the optimize settings in GIMP is settup first (Quality Settings) before you click the “SAVE” button. You will see the image result is optimized and you can upload it to your web server.
For WordPress blog, you can use Smush it plugin to make your image more optimize then before. Just install the plugin and under the plugin settings, find bulk smush it and click the button. All your image will be optimized.