I'm not sure what way steps you are trying but I usually click on 'Add reply' - which has the green cross - rather than 'Quick reply'
Look for 'Attachments' and on the extreme right of it on the screen you can see an arrow pointing to the left - click on it
Then click on 'choose file' and then once you've found your jpeg file click on 'Upload'
But you haven't finished yet! You can now see your file listed. Click on 'Insert Image' which is halfway across the screen but hard to see as the shading is harsh (I think this last part is where you are getting stuck)

Exactly as Jimbo says.

But there may be an issue with .jpeg.

Think it needs to be .jpg.

Easy to change.

Fred

This is for Windows.

Log on 

'Add Reply' on the picture below is just below your name on your message with the green and white plus sign

Now click on the small grey arrow that points to the left which is on the far right of your screen on the same line as 'Attachments'

 Click on 'choose file' and once you have selected it click on 'Upload' which has the green arrow pointing up

 Now click on the green and white plus sign in the centre of your screen which is on the same line as your filename to insert your image

Then click the 'Submit' button (which is a blue square) located to the left of the 'Cancel' icon

 Give up?? just a thought........

 I love a challenge!

https://www.youtube.com/watch?v=MWdewz2_jnk