do you have instruction to setup a timing belt for a 1987 volkswagen cabriolet

You have a timing mark in the camshaft and in the crankshaft. Look for the correct position. the crankshaft can be checked in the hole on top of the transmission. Be very careful because in the camshaft there may be several marks since different engines use this pulley. one easy way is to put the engine in TDC (be sure it is in compression) and notice that there is a mark in the camshaft that aligns to the border of the engine head, be sure that when you mount the belt the mark and the crankshaft are in the same position. And if you are changing the belt i recommend that you change the belt tensioner also.