Here are some screenshots I did a while ago to help with posting pictures.
You can either drag pictures directly into the post editor, or use the choose files option.
Using the choose files option you can select the picture(s) and they will appear at the bottom of the editor.
If you want the picture attached somewhere in the text, click on the place in the text you want to add it & click the + button on the picture.
You can also resize pictures when they are in the text by double clicking on them & editing the sizes.
Hope this helps.
David