My machine is currently being serviced - again!
But I know that the top tension is adjusted via the menu. But without having my machine in front of me, I can't exactly tell you how. Try the button with the tools on it - that might be the one. Then it's one of the top items listed in the menu.
There should be no need to adjust the bobbin tension. But if you wish to fiddle around with it - I would only do that as a last resort - you have to take the black bobbin-holder out and adjust the screw on its side. Be careful only to turn a quarter of a turn at a time and best mark the initial position as well.