can't find background image tab

If you know what iam talking about,iam currently using dark theme (hover on top profile name<<background<<dark)
i want to add a background image.. where can i find that option/tab?

Set it to transparent and upload your image.

it will say URL link and just put the url link to the photo

ah! got it. should have messed around a little more before asking on the forums but i could not find it in the Q&A page too. curse my ignorance :)