Click on Upload/insert or click the add media symbol which looks like this:
A new screen will pop-up which looks like this:
Click on “Select Files”
You can now select which images you want to upload from your computer. You can also link to files from other websites using “From URL” tabs, or you can select from previous uploaded images from “Media Library”.
You can now select how you want the image to appear in the post by selecting position, size, editing the image, and adding captions. Once you’re ready click the “Insert into Post” button
Images can be edited later using the Media tab on the Dashboard or by clicking on an image in a post and selecting the “Edit Image” symbol, shown below.