Adding your images will be different in WordPress. These will be images that you already have on your computer or that you will upload to your computer.
Pixabay.com is one I use the most to download images if I don't use a image from the media tab in SiteContent. I find a lot of pictures that are free.
When you go to pixabay.com you can search what type of picture you are looking for. Just don't click on one that has a yellow background as they are not free.
If you find one you like click on it and if you look to the right it will show if it is free with no attribute. You want to click the smallest size as the larger ones may load slow.
Having larger images on your website may cause them to load slower. Your visitors will not like that.
Depending on the option you chose when you have finished with your post/page in SiteContent you might have to login in if you did not choose the option to edit post in WordPres.
Click on website and then to the right you will see login. Since the release of the new UX this feature has made it a little more simpler than the previous way.
Once you log in you will notice the menu on your left. You will click on posts or pages depending what it is you need to add images to or edit.
Once you click on posts/pages you will click all posts/pages and then you can click on the title of the one you need.
If you hover over the title you will notice at the bottom there is edit, quick edit and delete. You can click on the title or click on edit.
When it brings up the post/page you are going to add an image to, you will notice it will have upload files and media library.