How do I optimize image already on my website?

[achizie]

Hello Dear,
Please, I want to know how I can use Online image optimizer to compress (optimize) some of the large images on my website. I tried using it, obtained the url from my site and pasted it, then selected jpeg and clicked optimize. It gave me a number of results starting from -8% to -87%.
I want to know what I should do next to effect this change, using, say, quality 50 (-69%) of the image on my website. Or does the change take place automatically?

Thank you.

[simon1854]

The % results are what file size it can reduce it by. What site are you using to do so? Essentially if wordpress for example, you have to re-upload your image to the website in the same place, if using FTP you have to re-upload the optimised image that way.

[achizie]

Thanks for your response. I am using Blogger platform.

[simonandrew89]

What are the file size you are using you can reduce the file size.