Optimizing image is very important for wordpress site. Image has a huge impact on speed of the site. A lot of images with larger files can slow down your site very badly. So, it is important to optimize and compress the image properly to reduces the sizes of the images. There is a very popular image compressor plugin available that is owned by Tiny PNG. It has a panda logo on the left upper side of the plugin. By using these plugin you can compress up to 500 images/month in free. If you need to compress more than 500 images/month, then you can join its premium plans. Here I will show you step by step of installing, setting and compressing process.
Full tutorial:-
- Go to the wordpress dashboard. Then go the add plugin option. search for Tiny PNG. You will see Plugin with Panda Image by TinyPNG. Click on install now

2. After installing click on Activate option.

3. Go the Installed Plugin option. Then go the setting of compress jpeg and png images that is owned by Tiny PNG.

4. Register for a new account. Enter your name and Email address. Click on Register account.

5. It will show that a email has been sent to activate your account.

6. Now go to your gmail account. Activation mail will come within few seconds. open the mail of tiny image. Click on activate your account.

7. You account will be activated and you are being redirected to the tiny account. Then Click on Vertical 3 dots.

8. Click on Enable key.

9. You will see a API key. Return to the wordpress dashboard tiny png setting. Enter the API key and Save.
N.B. Maximum times it will detect API key automatically if not then manually copy API key from that tiny account and paste it inside setting of Tiny PNG. and Save it.

10. You will see a message that your account is connected and you can compress up to 500 images/month.
Select Compress new image during upload.

11. Tick only on Original Image and deselect other options. If you tick others options then you cannot compress 500 images/month.

12. Then click on save changes.

13. Now I am showing you the size after compress. Add a image in the media of wordpress dashboard.

14. Image Size is 67.3 KB.

15. Now the size is 55 KB after compress.

To be frank The image i used for compressing it was already compressed before. I am showing you as a example to make you understand.
This is the full tutorial of Image optimization and compression by tiny PNG. If you do not follow above steps you may not optimize 500 images/month. Please feel free to share your comments.