Have you got it together yet?
If not, did you try google image searching for 'Playmobil 3773'? There are lot of images that should help you.
If I had the instructions I would send them, but while I do have a 3773, it is not in box and I am sure the instructions are not present (actually, I have never set it up yet). I have the 3806 (Fort Glory) in box (again, never set it up either) - so it should have instructions. It looks close in configuration - does anyone know if they are the same in layout?
I also have 3419, Fort Randall, again never set up.
I was going to combine them to make a super fort but time has given precedence to more pressing matters.