First step, insert your written text into the white comment box.
Next click the 'Attachments and other options' line and you will see:

Click Chose File and select the photo you want from your desktop. You will see the file name appear in place of 'No File Chosen.
If you hit post at this point, your photos will all appear at the end of your post.
You can change the 'End-of-post-expandable-thumbnail' by clicking on the down arrow. Position your cursor at the point in the post you want the photo to appear and then change the 'End-of-post-expandable-thumbnail' to 'Inline full size image' this positions the photo at the point you place the cursor.
It is up to you how you arrange the photos within or at the end of the post
I hope this helps.