The simple and easy way is use a free host site such as Imgur.
Create a free account, upload the pics to your host account, copy the BBCode link, paste the link here in the text box. Pics need to be .jpg, .gif or .png file types.
The links (URLs) should have IMG tags like this-
[img]https://i.imgur.com/3BlA71j.jpg[/img]This will show the picture in-line with the body of the post like this without needing to click on links to go off-site-
Don't use social media hosting such as iCloud, Facebook or Google as those seem to have a lot of problems with showing pictures here.