You've probably got three scart leads and a maybe couple of thinner ones depending on the model of STB you've got and whether or not you still use your roof aerial.
The first scart lead needs to go from the bottom socket on your STB (should be labelled TV) to the AV 1 socket on your TV.
The second goes from the top socket on your STB (should be labelled VCR) to the your DVD recorder (Not sure which socket but the instructions for it should be able to tell you.
The third (which may say DVD on it) goes from the other socket on your DVDR to the AV 2 socket on your TV. If this one does actually say DVD on it then it will only work properly if the ends are connected the right way round, again they usually have printed on them which end goes into the TV and which goes into the DVDR.
As for the thin ones then there may be one which goes from the aerial socket on the STB to the aerial in socket on the DVDR and then another which goes from the aerial out socket on the DVDR to the aerial socket on the TV.
There's a couple of pictures of it all floating about on the site, if I can find one of them I'll post the link.
link thingy This page is about getting the FM radio channels through cable but it does show you how the thinner coax cables should connect, just replace the VCR in the pics with your DVDR