There should be a series of switches on the back panel if (after you sit down) you turn your head about 150 degrees to the right. This is from Naverkehr Dresden in TSW2, I didn't realise that the Dostos were updated in TSW3, nor do I know whether my instructions are rendered useless by it.
I saw it on there once from Nahverkehr Dresden, but LZB doesn't work on these one's, I thought it would work on the one from Kassel-Würzburg