You can only see the various editing control buttons, such as "Quote", "Insert Image", "Bold" etc, when in editing mode.
If you want to insert and image in a post that you made earlier then you should select:
More > Edit Post
and you will be able to make changes to your post. (You can't edit other people's post, unless an administrator with the appropriate permission set.)
Volunteer Helper - but recommending that users move off the platform!
Once the admin for GregHelp now deleted.