#1 have a picture that is in .png or .jpg or .jpeg format, then click on the Icon below the editor that looks like a miniature mountain landscape. that will offer you two options, 3 actually... but the most simple is to click in the center of the new Landscape icon and browse your PC until you find the pictures. You can click on more than one if you like, just hold down the Control Key and add more... but that will jumble them all together. It is better to add one picture and then type some words to describe that one picture.
Note that you can also Drag 'n Drop a picture.... I tried that, and the location where it drops the picture is not where I want the picture, so I never use that method.
then hit <return> 3 times to give some space between that picture and the next picture and repeat.
#2 when the Landscape Icon opens up, there is a figure-8 that allows you to use a URL to the location of the picture you have hosted elsewhere.... such as Imgur.com or any other place.
#3 Cellphones are somewhat the same, this is a picture of the editor from my cellphone just now.
just follow the prompts, it should be the same as I described.