Pasting an image from computer's drive

Quoting from the tutorial above:
Next, highlight the address of the picture you want to post (just click on the box that contains the address to highlight it)
and then Copy that using your system's copy command (e.g. Control plus C). Then Paste it in using your paste command (e.g. Control plus V).

I am not sure or If I missed the information on where to paste the address of the picture. Can anyone help?

Thanks in advance!

Paste it into the draft post you wish to include it in.