Right click on the directory, and at the bottom you will see Properties. Click that, and you should see a set of 3 by 3 tick boxes.
Somewhere toward the bottom (if I remember correct) it should have these numbers (i.e. 755 or something).
Then just click the empty boxes to change properties according to what you need/want.
However, it may not be this either...
This thread shows what others have done