It's important to optimise photos and other graphics before adding them to a website. There are plugins available to do this automatically, but I prefer to optimise images before they are introduced to the site, using Photoshop.
If you're serious about blogging for income, you'll probably need to learn to use professional graphics software like Photoshop or Affinity Photo, at some point.
However, if you don't have access to graphics software like Photoshop, Affinity or some other software right now, you can still optimise images easily online.
The online method I recommend is free and doesn't require you to sign up to a website or do anything fancy. I'll show you how to use it.
Imgix is a special service for software developers, but they have a free practice area called a sandbox that we can use to optimise our images.
Go to Imgix to get started.
Next, follow the instructions in the above video. Imgix enables you to take a huge image, straight out of your camera or downloaded from a stock image website, and very easily obtain a small, lightweight file that can be used on your site.